Updating Windows is very important for the system. If the Windows update process is delayed, it can pose a threat to the system, so this issue should be addressed as a priority. However, the update does not always go smoothly. Sometimes an error occurs that prevents the update from completing. One of the common Windows update errors is 0x80071a91.

Please read the post on Thewindowsfan.com today to discover how to fix this problem.
1. Reset service FSRM
The underlying cause of the error is an interrupted File System Resource Manager (FSRM) service. Therefore, try resetting this service via Command Prompt with admin rights.
Open Command Prompt with admin rights. Type the following command into the Command Prompt window and press Enter to execute:
fsutil resource setautoreset true C:
Once the command has been executed, reboot the system and check if it helps to fix the problem.
2. Turn off antivirus protection temporarily.
Antivirus software may be preventing Windows Update from working properly. Therefore, you can turn off the antivirus program for a while and see if that helps.
3. Reset the Windows Update components
Reset Windows Update components can help with this error.
4. Clearing the Common Log File System (CLFS) transaction log
Open Command Prompt with admin rights. Type the following commands one by one and press Enter after each to execute:
cd /d %SystemRoot%System32SMIStoreMachine
attrib -s -h *
del *.blf
del *.regtrans-ms
Check to see if you can upgrade Windows after restarting the system.
5. Run the Windows Update Troubleshooter

Select Windows Update Troubleshooter and run it.
6. Restart Windows Update services
Open Service Manager, make sure they are started, and the corresponding startup types of these services are as follows:
- Background Intelligent Transfer Service: Manual
- Cryptographic Service: Automatic
- Windows Update Service: Manual (Triggered)
I hope this information is useful to you.