SOLVED
I have a Windows 10 PC which was linked to my work Office 365 account and it was connected to Windows Insider for Business program. I can login with this account to Insider for Business page and it says i'm already registered. This PC was offline for a while and there were probably 5-10 builds during that time. I have turned it on and it installed a few builds (not the latest for some reason) and then it just showed that there was a problem with my MS account, but when i try to enter my credentials it shows error that something went wrong and i should try later (can't even close this warning).
I guess will have to reinstall this PC from scratch (not a first time it gets bugged after a few build updates)..
