How to fix windows 11 update error 0x800f0991?

There are some methods you can try to fix the Windows 11 update error 0x800f0991 that are less commonly known. Here are a few options:

1. Use the Windows Update Log and DISM Logs for Advanced Diagnostics

• Navigate to the Windows Update log by running the command Get-WindowsUpdateLog in PowerShell.
• Analyze the log files for specific clues about the error.
• Similarly, check the DISM log located at C:\Windows\Logs\DISM\dism.log for detailed errors that can guide targeted fixes.

2. Manually Repair System Image Using DISM with a Source

• Sometimes, the error occurs due to corrupted system files or missing updates. You can manually repair the system image by pointing DISM to a known good source, such as a Windows ISO.
• Download a Windows 11 ISO matching your current version, mount it, and run: DISM /Online /Cleanup-Image /RestoreHealth /Source:X:\Sources\install.wim /LimitAccess
• Replace X: with the mounted ISO drive letter.

3. Use the Windows Update Troubleshooter in a Command Line Mode

• Run the troubleshooter from an elevated Command Prompt with: msdt.exe /id WindowsUpdateDiagnostic
• This can sometimes fix the Windows 11 update error 0x800f0991 that the GUI troubleshooter misses.

4. Reset Windows Store and Related Components

• Since some updates depend on the Windows Store, resetting it might help: wsreset.exe
• Also, re-register Windows Store apps: powershell -ExecutionPolicy Unrestricted -Command & {Get-AppXPackage *WindowsStore* -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register "$($_.InstallLocation)\AppXManifest.xml"}}