I'll give you the fixes that work most for Windows Update failure, which include going over the system to find and fix all problems:
1) See if you can System Restore to a point before the problem started: https://itechhacks.com/system-restore-windows-11/
System Restore is your first line of defense and can take you back to a point before a problem began like a time machine. If it doesn't help then you can undo it. Read about it first in the tutorial above and then try restoring to just before this started. If System Restore is not enabled on C drive do that now so it's available in the future.
If the problem repeats or System Restore doesn't work then check which Windows Updates were installed at Settings > Update & Security > Windows Updates > Update History, uninstall them there or System Restore again, then immediately check for and block the Updates with the Hide Updates tool explained here: https://www.droidwin.com/how-to-stop-only-a-specific-update-from-installing-in-windows-11/
2) You can install the Updates that fail to install manually and sometimes this will fix Updates, too. Failed updates should be logged at Settings > Update & Security > Windows Update > Installed Update History, and then search for those to download and install from this Catalog: https://www.catalog.update.microsoft.com/Search.aspx?q=%20Windows%2010
Some Updates will sort themselves out in a few days. If not or they are bothering you then continue with the steps.
3) Run the Windows Update Troubleshooter from Windows Settings > Update & Security > Troubleshoot.
4) Type Services in Search box, run Services app as Administrator, open Windows Update Service and Background Intelligent Transfer Service and Stop both. Press “Windows (flag) key + R,” copy and paste C:\Windows\SoftwareDistribution\ and press the Enter button. This folder has all the files related to Windows updates.
Open the “Download” folder, select and delete all the files.
Restart Windows Update and Background Intelligent Transfer services in Services app by opening both and choosing Start.
5) If that fails try manually resetting Windows Update Service with the commands here: https://www.askvg.com/fix-windows-update-problems-using-automatic-reset-script/
6) Try these latest fixes for Updates not installing in Windows 11:
https://www.elevenforum.com/t/reset-windows-update-in-windows-11.3808/
https://windows101tricks.com/windows-11-update-failed/
https://www.anoopcnair.com/fix-windows-update-issues-for-windows-11-errors/
https://www.youtube.com/watch?v=r_Xuk-8iAPg
https://www.youtube.com/watch?v=-g-QXG4Nsac
7) If they continue to fail and interfere, then you can block them using one of these methods: https://www.droidwin.com/how-to-stop-only-a-specific-update-from-installing-in-windows-11/
8) Download, install and run a full scan with the most powerful on-demand free scanner Malwarebytes from https://www.malwarebytes.com/mwb-download/. Enable Root Kit scanning in it's Scan settings. You can turn off the free trial in it's Account Settings if you want to keep it, which I would do because nothing else comes close to its thoroughness. But you don't need the Real Time protection if you don't get routinely infected.
Clean up anything found, restart PC and then run again until it comes up clean.
9) Establish a Clean Boot to get rid of Startup freeloaders that can hog resources and cause issues by conflicting: https://www.makeuseof.com/clean-boot-windows-11/
10) Run Windows 11 System File Checker/DISM in WIndows 11: https://www.elevenforum.com/t/use-system-file-checker-sfc-to-repair-system-files-in-windows-11.720/
11) If that doesn't fix it then you can do a Windows 11 Repair Upgrade: https://www.elevenforum.com/t/repair-install-windows-11-with-an-in-place-upgrade.418/
12) For sluggish Updates, try turning on Delivery Optimization in Settings > Windows Update > Advanced Options? This creates a torrent that bounces pieces of the update off of nearby PC's so that you collect it more gradually and in the background. MVP's didn't like it because of stability-related issues when it first came out in early Windows 10, but it's matured a lot lately, so worth a try.
If you were referred here from another thread, please post back results in that thread. Otherwise you can ask questions and share information in the Comments section below.
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