Fix KB5016691 for Windows 11 for x64 failing to install, Fix Update KB5016691 Not Downloading/Installing Update KB5016691 On Windows 11, Cumulative Update for Windows 11 for x64-based Systems (KB5016691) Stuck Downloading, Fix Can't Update Windows 11 with KB5016691 Update
Step 1) Run Update Troubleshooter
Step 2) Restart Windows Update & Background intelligent transfer service
Step 3) Use Windows 11 Installation Assistant https://www.microsoft.com/en-us/software-download/windows11
Step 4) Use Microsoft Update Catalog https://www.catalog.update.microsoft.com/Home.aspx
Step 5) Reset Windows Update Components
SC config trustedinstaller start=auto
net stop bits
net stop wuauserv
net stop msiserver
net stop cryptsvc
net stop appidsvc
Ren %Systemroot%\SoftwareDistribution SoftwareDistribution.old
Ren %Systemroot%\System32\catroot2 catroot2.old
regsvr32.exe /s atl.dll
regsvr32.exe /s urlmon.dll
regsvr32.exe /s mshtml.dll
netsh winsock reset
netsh winsock reset proxy
rundll32.exe pnpclean.dll,RunDLL_PnpClean /DRIVERS /MAXCLEAN
dism /Online /Cleanup-image /ScanHealth
dism /Online /Cleanup-image /CheckHealth
dism /Online /Cleanup-image /RestoreHealth
dism /Online /Cleanup-image /StartComponentCleanup
Sfc /ScanNow
net start bits
net start wuauserv
net start msiserver
net start cryptsvc
net start appidsvc