How to fix
Windows Update error 0x80071A91
on Windows

I cannot download any Windows updates. Update search ends up with an error code 0x80071A91 all the time. Does someone know what should it to fix it?

Error Code 0x80071A91 is a Windows 10 problem, which prevents people from installing updates using automated Windows Update[ref en-1] service. Despite many warnings expressed by cyber security experts on the Internet, many people are still keeping updates aside without considering what consequences outdated system may have on its performance and security.

Keep in mind that automatic Windows Update feature ensures the installation of Windows Defender definitions,[ref en-2] security patches, feature updates, performance udpates, and so on. Therefore, although indirectly, the prolonged existance of the error code 0x80071A91 can leave the system vulnerable and rather sluggish.

Several people reported that methods that normally help to fix Windows Update problems did not help to fix 0x80071a91 error. Running Windows Update Troubleshooter, resetting Windows Update components didn't do the trick. That's because this bug is usually related to File System Resource Manager (FSRM),[ref en-3] which might have been disabled by mistake. Besides, it may be triggered by Common Log File System (CLFS) transaction log files.

Thus, FSRM reset should be the initiate step towards 0x80071a91 error fix. If that did not work, proceed with the removal of the CLFS transaction logs. Finally, try methods that are typically applied for the removel of Windows Update problems.

Reset FSRM

• Press Windows key and type cmd.
• Right-click on the search results and select Run as Administrator.
• Alternatively, you can right-click on Windows key and select Command Prompt (Admin).
• Now copy and paste the fsutil resource setautoreset true C:\\ command in Command Prompt. (C: stands for the root drive of the system, so change it if needed).

• After the command is being executed, restart the system and check if Windows Update service works.

Remove Common Log File System (CLFS) transaction logs

• Press Windows key and type cmd.
• Right-click on the search results and select Run as Administrator.
• Alternatively, you can right-click on Windows key and select Command Prompt (Admin).
• Once Command Prompt window opens, copy and paste the commands given below. Don't forget to press Enter after each of them:
  
  cd /d %SystemRoot%\\System32\\SMI\\Store\\Machine
  attrib -s -h *
  del *.blf
  del *.regtrans-ms
  
  
• Once the commands are executed, close Command Prompt and restart your PC. Check if this method worked and fixed the 0x80071a91 error.

However, many people reported that the above-listed commands cannot run because the executable files are in use, you may need to install Unlocker utility. Once downloaded, follow these steps:

• Press Windows key + R, type %SystemRoot%\\System32\\SMI\\Store\\, and press Enter.
• Right-click on the Machine folder and select Unlocker.
• Select Unlock All.
• Once done, try to perform the steps provided above.

If these two methods did not work and you are still facing error code 0x80071a91, try the methods that are known for fixing most of Windows Update bugs. You can find them all here.