How to fix "Installation has failed" error in Microsoft Teams?

Installation has failed is the generic error window of the Teams setup file, so the real reason is written in its setup log. Most often an old or half-installed Teams, a second running setup or an outdated installer blocks the new Teams package. Close every setup, delete the SquirrelTemp folder and run one fresh installer from Microsoft (Fix 1).

Facts checked on 15 October 2026. Steps written for the new Microsoft Teams (MSIX package) installed with MSTeamsSetup.exe and teamsbootstrapper.exe on Windows 11 (25H2 and 26H2) and Windows 10 22H2, read against Microsoft's documentation.

What "Installation has failed" means in Microsoft Teams

You double-click the Teams setup file, a small splash appears for a few seconds, and then a window with a red cross says Installation has failed. Under it: There was an error while installing the application. Check the setup log for more information and contact the author.

The wording is not Microsoft's. It is the stock failure message of Squirrel, an installer framework for desktop apps. Classic Teams used it, and the current MSTeamsSetup.exe still starts it: the first log line reads "Starting Squirrel Updater: --install . --exeName=MSTeamsSetup.exe --bootstrapperMode". That is why the same window appears for Discord and GitHub Desktop.

Check the setup log: where the real cause of the Teams error is written

The message tells you to check the setup log, and that advice is right. Select Open Setup Log in the error window, or open the file yourself. It is plain text and opens in Notepad.

1. Press Win + R, paste this path and press Enter:

   %LocalAppData%\SquirrelTemp

2. Open SquirrelSetup.log. The newest attempt is at the bottom.
3. Press Ctrl + F and search for error, then for exception.
4. Compare the line you find with the picture below and start with the fix it names.

What causes the Teams Installation has failed error, ranked

Microsoft does not rank these causes. The order below is our reading of the setup logs posted on Microsoft Q&A and of what Microsoft documents about installing new Teams. It is not a statistic.

Microsoft's status: classic Teams retired, new Teams and Windows 10

• Classic Teams is gone. Microsoft ended support for classic Teams on 1 July 2024 and its availability on 1 July 2025. An old Teams_windows_x64.exe installer saved on your PC is not a way back.
• New Teams is a Windows app package. It installs as the MSIX package MSTeams and keeps its data under %LocalAppData%\Packages\MSTeams_8wekyb3d8bbwe. That is why package policies and package registration matter.
• Two installers. Microsoft's download page gives you MSTeamsSetup.exe, which installs the new Teams for your account. Administrators can use teamsbootstrapper.exe for the whole PC (Fix 4).
• Windows 10 is still listed. Teams' system requirements, read on 15 October 2026, ask for Windows 10 version 10.0.19041 or higher, excluding LTSC. Windows 10 itself left support on 14 October 2025, so keep in mind that future Teams versions may drop it.
• Minimum hardware. 4 GB of RAM, 3 GB of free disk space and a two-core 1.1 GHz processor.

To see your Windows version, press Win + R, type winver and press Enter. Windows 10 version 2004 or later and every Windows 11 version meet the build requirement. If you cannot install Teams at all, Teams on the web at teams.microsoft.com works in current Edge, Chrome and Firefox.

How to fix Installation has failed in Microsoft Teams

Read the setup log first if you can, then start with the fix it points to. Without a log, go in order and run the installer again after each fix. Success looks the same every time: the setup closes on its own and Teams opens its sign-in window.

Fix 1. Close every setup, clear SquirrelTemp and run one fresh installer

5 minutesNo riskEveryone, first. Above all when you started the setup more than once or saved the file a while ago.

The setup engine breaks when two copies run at once and leaves its files in SquirrelTemp. A freshly downloaded installer also asks Microsoft for the current Teams package instead of an outdated one.

1. Close every error window. Right-click the Teams icon in the taskbar corner, if there is one, and select Quit.
2. Press Ctrl + Shift + Esc, and under Processes end every MSTeamsSetup, Teams or Update.exe entry that is left.
3. Press Win + R, paste this path and press Enter. Delete everything in the folder:

   %LocalAppData%\SquirrelTemp

4. Delete all old Teams setup files in Downloads, including copies named MSTeamsSetup (2).exe or similar.
5. Download the installer again from Microsoft's page: https://www.microsoft.com/microsoft-teams/download-app.
6. Right-click the new file, select Properties and, if you see it, tick Unblock and select OK.
7. Double-click the file once and wait. Do not start it again while the splash screen is visible.

If it fails again, try once with Run as administrator from the same menu, as Microsoft staff suggest. Expect little from it: the new Teams installs per user, and one posted log shows the setup restarting itself with the flag --rerunningWithoutUAC.

Fix 2. Uninstall classic Teams and the Teams Machine-Wide Installer

10 minutesLow riskClassic Teams, the Teams Machine-Wide Installer or an older Microsoft Teams entry is still in your list of apps.

Microsoft staff name remnants of a previous Teams installation as a cause of the registration failure. Classic Teams also left a per-user folder that the new setup does not clean up.

1. Quit Teams from the taskbar corner.
2. Open Settings > Apps > Installed apps and type Teams in the search box.
3. Uninstall Microsoft Teams classic, Teams Machine-Wide Installer and any Microsoft Teams entry with a version that starts with 1. Keep Microsoft Teams (work or school) only if it opens.
4. Press Win + R, open this folder and delete it if it exists:

   %AppData%\Microsoft\Teams

5. Do the same with the second folder:

   %LocalAppData%\Microsoft\Teams

6. Restart the PC and run the installer as in Fix 1.

Every uninstall route, with the Windows 10 screens: Uninstall a program or app in Windows. The two folders hold the old app and its cache. Microsoft's cache article lists %appdata%\Microsoft\Teams as the classic Teams cache, so deleting it loses nothing that the new Teams uses.

Fix 3. Remove a stuck MSTeams package with PowerShell

10 minutesLow riskSquirrelSetup.log shows Registration error, Registration failed or 0x80070003, or Teams is half installed and will not open.

The setup stages the package and then registers it. When an earlier MSTeams package is half registered, for you or another account, registration fails three times and the window appears. Microsoft's uninstall article gives the commands that remove it.

1. Quit Teams and close any setup window.
2. Right-click Start and open Terminal or Windows PowerShell.
3. List the Teams packages for your account:

   Get-AppxPackage *MSTeams*

4. Remove them for your account:

   Get-AppxPackage *MSTeams* | Remove-AppxPackage

5. Close the window. Right-click Start again and open Terminal (Admin). Select Yes in the User Account Control prompt.
6. List the package for every account on the PC. A result here that you did not see before belongs to another account:

   Get-AppxPackage *MSTeams* -AllUsers

7. If you share the PC and nobody else needs that copy now, remove it for all accounts:

   Get-AppxPackage *MSTeams* -AllUsers | Remove-AppxPackage -AllUsers

8. Restart the PC and run a fresh installer as in Fix 1.

Fix 4. Install Teams for the whole PC with teamsbootstrapper.exe

10 minutesLow riskMSTeamsSetup.exe keeps failing, you have an administrator account, or you manage several PCs.

This is Microsoft's own command-line installer for the new Teams. It provisions the MSIX package for every account on the PC, replaces other Teams versions and prints a clear success or error code instead of the generic window.

1. Download teamsbootstrapper.exe from Microsoft: https://go.microsoft.com/fwlink/?linkid=2243204.
2. Right-click Start and open Terminal (Admin), then select Yes.
3. Go to the Downloads folder:

   cd "$env:USERPROFILE\Downloads"

4. Provision Teams for all users:

   .\teamsbootstrapper.exe -p

5. Read the result. A success line means Teams is installed: start it from the Start menu.
6. If you get an error code instead, look it up in Microsoft's list of common HRESULT values or send it to IT.

Fix 5. Check the app package policies that block new Teams

10 minutesLow riskA work or school PC, the message "Due to org policy, you can't install the new Teams", or an administrator suspects a policy. Editions with Group Policy only.

New Teams is an MSIX package, and Microsoft names two Group Policy settings that can block such packages. If Allow all trusted apps to install is disabled on an older build, the installation fails.

1. Press Win + R, type gpedit.msc and press Enter.
2. Go to Computer Configuration > Administrative Templates > Windows Components > App Package Deployment.
3. Open Prevent non-admin users from installing packaged Windows apps and make sure it is Not configured.
4. Open Allow all trusted apps to install and make sure it is Not configured.
5. Select OK, restart the PC and run the installer again.

More about the editor: Open the Local Group Policy Editor. Microsoft lists the registry values behind these policies, BlockNonAdminUserInstall, AllowAllTrustedApps and AllowDevelopmentWithoutDevLicense, under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\AppModelUnlock and HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Appx. Look at them only; if you must change one, first Back up the registry before editing it.

Fix 6. Install Windows updates and repair system files

20 to 30 minutesNo riskOther Store apps fail to install too, Windows has pending updates, or the log shows an exception that none of the earlier fixes explain.

Microsoft fixed one known block of the Teams package in the October 2023 updates KB5031455 for Windows 11 and KB5031445 for Windows 10, and its troubleshooting page says to install pending updates first. Microsoft staff also suggest DISM and SFC when package registration fails.

1. Open Settings > Windows Update and select Check for updates. Install everything, including security updates, and restart.
2. Open Terminal (Admin) and run DISM, then SFC, as the procedure below shows.
3. Restart the PC and run the Teams installer as in Fix 1.

1. Open an elevated command window. Right-click Start and select Terminal (Admin), or type cmd in the search box, right-click Command Prompt and select Run as administrator. Select Yes when Windows asks for permission.
2. Run DISM first. Type the command below and press Enter. DISM downloads clean copies of damaged components from Windows Update, so it can take several minutes. Wait until it says The operation completed successfully.

   DISM.exe /Online /Cleanup-Image /RestoreHealth

3. Run System File Checker. In the same window, type the command below and press Enter. Do not close the window until the verification reaches 100%.

   sfc /scannow

4. Read the result and restart. Compare the last message with the table below this guide, then restart the PC so that repaired files are loaded.

These steps were written for Windows 11 24H2 and 25H2. The full page with the other versions and what each result means: Run DISM and SFC to repair Windows system files

Fix 7. Pause third-party security software for one install

5 minutesLow riskThe log stops at the download, or no SquirrelSetup.log appears at all, and other fixes did not help.

In the most upvoted answer of a 2022 Q&A thread a user ended the error by stopping the antivirus services, installing Teams and turning them back on. That is a user report, not a Microsoft finding, so use it as a test only.

1. Pause the protection of your security program for a few minutes from its own icon. For Microsoft Defender use Turn off Microsoft Defender protection for a moment.
2. Run the freshly downloaded installer right away.
3. Turn the protection back on as soon as Teams opens, or after 10 minutes at the latest.
4. If this was the cause, add the Teams installer to your security program's allow list instead of pausing it next time.

Fix 8. Test the install in another Windows account

15 minutesNo riskThe setup fails only for you, other accounts on the PC have Teams, or every fix above failed.

Teams installs per user, so a damaged user profile or a package held by another profile breaks only some accounts. In the July 2026 Q&A case the error ended once a second Windows profile with Teams files was removed.

1. Create a new local test account with administrator rights, as Create a new user account to test a problem shows.
2. Sign out and sign in to the test account.
3. Download the installer from Microsoft and run it once.
4. If Teams installs there, the problem is tied to your own profile. Go back to Fix 3 and remove the package for all users, then try your own account again.
5. Delete the test account when you are done, in Settings > Accounts > Other users.

If Teams still will not install: what to collect and who can help

If all eight fixes failed, stop changing the PC and collect the evidence. Microsoft support or your IT department can read it in minutes, and you can keep working in Teams on the web meanwhile.

• SquirrelSetup.log from %LocalAppData%\SquirrelTemp, from the latest attempt.
• AppxDeployment-Server errors from Event Viewer at the same time, exported or as a screenshot.
• The output of Get-AppxPackage *MSTeams* -AllUsers in an admin terminal. Microsoft staff ask for it before anything is removed.
• Your Windows version from winver, and whether the PC is managed by an employer or school.
• For administrators: Microsoft's Teams preinstallation check script at https://aka.ms/NewTeamsReadinessCheck lists what blocks the install and suggests a solution.

How to keep Teams from failing to install again

Frequently asked questions

What does "Installation has failed. There was an error while installing the application" mean in Teams?

It means the Teams setup file could not finish installing, and that the window itself does not know why. The message is the stock text of Squirrel, the installer framework that MSTeamsSetup.exe still starts before it installs the new Teams package. The reason is written in SquirrelSetup.log in %LocalAppData%\SquirrelTemp. Most often the package was downloaded but Windows could not register it, because an older or half-installed Teams is still on the PC.

Where is the Teams setup log?

In %LocalAppData%\SquirrelTemp\SquirrelSetup.log. Press Win + R, paste %LocalAppData%\SquirrelTemp and press Enter, then open the file in Notepad. The Open Setup Log button in the error window opens the same file. The newest attempt is at the bottom. Search it for error and exception. If the log names a registration problem, Event Viewer holds more under Applications and Services Logs, Microsoft, Windows, AppxDeployment-Server, Operational.

Why is Microsoft Teams not installing on Windows 11?

Windows 11 meets every Teams requirement, so the cause is almost always on the PC itself. The usual reasons are leftovers of an earlier Teams, a second copy of the setup running, an old installer file, a package policy on a work PC, or damaged app deployment parts. Start with Fix 1 on this page: close everything, delete the SquirrelTemp folder and run one fresh installer from Microsoft. Then follow the line in SquirrelSetup.log.

Can I still install Teams on Windows 10?

Yes, on Windows 10 version 2004 (build 19041) or later. Microsoft's Teams system requirements, read on 15 October 2026, still list Windows 10 10.0.19041 or higher, except LTSC editions. Windows 10 itself left support on 14 October 2025, so later Teams versions may drop it. On Windows 10, the message "We've run into an issue" is a separate problem: Microsoft says to install the WebView2 Runtime and start Teams again.

What does error 0x80070003 in the Teams setup log mean?

0x80070003 is the Windows error "The system cannot find the path specified". In SquirrelSetup.log it appears as "Package could not be opened" with AppxManifest.xml, after the package was staged. Windows could not register the Teams package for your account. Microsoft staff tied it to remnants of a previous Teams or to the Windows app deployment parts. Remove the MSTeams package for all users with Fix 3, then install again.

Can I still download classic Teams instead?

No. Microsoft ended support for classic Teams on 1 July 2024 and ended its availability on 1 July 2025. An old Teams_windows_x64.exe or a classic Teams entry with a version starting with 1 should be removed, not reinstalled. The current installer from Microsoft's download page installs the new Teams. If the new Teams cannot run on your PC, use Teams on the web.

How do I repair a Teams installation that half worked?

If Teams appears in Installed apps, open its three dots menu, select Advanced options and try Repair, then Reset. Microsoft notes that Reset deletes the app data, including your Teams settings. If Teams does not start at all or the setup keeps failing, remove the package with Get-AppxPackage *MSTeams* | Remove-AppxPackage, as in Fix 3, and install again from Microsoft's page. Chats and files are stored in the cloud and come back after sign-in.

Do I need administrator rights to install Teams?

Not for MSTeamsSetup.exe: the new Teams installs per user, and one posted log shows the setup restarting itself without elevation. Running it as administrator rarely changes the result. You do need administrator rights for teamsbootstrapper.exe, which installs Teams for every account on the PC, for removing a package for all users and for the policy checks. On a work PC without those rights, ask IT.

Is turning off the antivirus a good fix for this error?

Only as a short test. In a 2022 Q&A thread a user ended the error by stopping the antivirus services during the install and turning them back on afterwards. Microsoft does not name security software as a common cause. Pause protection for one install of a file you just downloaded from microsoft.com, turn it back on right after, and add the installer to the allow list if that was the cause.

Why does the same Installation has failed window appear for Discord or other apps?

Because Discord, GitHub Desktop and other desktop apps use the same Squirrel installer framework that the Teams setup starts. The window and its text are the framework's, so they look the same everywhere. The causes are similar too: two setups running at once, leftovers in SquirrelTemp or a blocked download. This page covers Teams, but Fix 1 and the log check work the same way for those apps. This error has the same text in every language edition of Windows.