I'm having the exact same issue on an MSI PRO Z690-A WIFI. Had a Windows 11 installation upgraded from 10, upgraded from 8. Everything was working just fine, Windows was fully activated... until I updated the BIOS. Now I'm getting the same activation error. When I go to "I changed hardware recently" I can select my desktop with the correct motherboard shown, but when I click "Activate" it says "we can't activate your copy of Windows as the digital license for this device has already been used to reactivate Windows" - which is true. I used it 2 days ago when I did a fresh install of Windows 11 upgrading from Windows 10. This is the same motherboard though, not a new system!
So far Support has told me that it might work to reinstall Windows 8(!), reactivate using the original product key from when I bought the computer, and then upgrade to Windows 11 from there. No, thank you - not after I just spent days getting Windows 11 properly set up.
Absolutely ridiculous....