I found a similar thread with someone saying he couldn't update on Windows 8.
I have the same issue here, but it started with Windows 8 not accepting my key after a restart. Now the Windows 8 I used was downloaded from the link in my receipt email, and the 8.1 from the Windows Store with normal procedures. It's the second time I clean installed them but the first time I did it through UEFI. Now after a reboot – as I mentioned – Windows says my key was for non core upgrade procedures and not clean install ones, so I followed another post on Microsoft's community, which said it was a common problem and you could solve it by changing the
mediabootinstall DWORD 32 bit key value to zero and then
slmgr -rearm in an elevated prompt.
Which I did and I was able to enter my key again, but now when I update I get the code 800f0922 on all updates – and I've already tried a clean boot but it didn't work.
So my problem is: I can't update and Windows doesn't accept my key. There is no chance my key got compromised or anything like that.