That’s frustrating. Anything unusual about your network, or Region settings? Are you using a VPN (maybe disable it)? or custom DNS? Not sure what else it could be.
If I was in your position I would be considering erasing the computer and doing a fresh generic install of Windows (but that’s just my personal way of dealing with trouble like that). I’m sure there must be a solution that doesn’t require a full PC reset… hoping someone else will have better insight for you.
Edit - in another thread, full screen mode was an issue for login… maybe try Alt Enter (key combo to switch between full screen and window mode)?