I get error code 0x800f0991 I'm investigating the issue and found that I need to disable Windows Sandbox, which is already turned off. Alternatively, I could perform an in-place upgrade, but that option is only available for the regular Home and Pro versions.
You need to build an iso with all of the updates included. Then, perform the in-place upgrade repair. (I've had to do it two months in a row now on a few machines - not exactly sure why.) If necessary, grab an official 26100.1742 iso from here: https://forums.mydigitallife.net/th...-2024-24h2-26100-x.88280/page-95#post-1854338 You can integrate the updates using the W10UI utility by @abbodi1406 here: https://forums.mydigitallife.net/posts/1216064/ Basic instructions for integrating the latest updates have been posted by @Enthousiast here: https://forums.mydigitallife.net/threads/windows-11-hotfix-repository.83741/page-147#post-1875482 If W10UI is too complicated, grab NTLite Free version and integrate the updates into the iso that way. (Some MDL hardliners don't like NTLite, and you won't get support for using it here on MDL. However, I've personally had better luck using it to update iso files than the W10UI way.)
Using an updated iso is the only way I know of to perform an in-place upgrade repair install on LTSC. I don't think the Windows Update Assistant will work, nor will the "Fix problems using Windows Update" in Settings. Your options beyond mounting an iso are to reset or reinstall the OS. (I'm assuming the routine sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth commands didn't help.)