Windows login refuses AD and local accounts, asks for MS Live account

Today, two of my machines have received Windows updates and rebooted. After rebooting, the login screen showed both my username as well as an inputbox for username and password, which struck me as odd (usually it's only password if the username is displayed).

I tried to log in with the usually logged in domain user, but I could not log in. I tried my own (domain administrator) account, which could not log in either. Finally, I tried the local administrator account (yes I specified .\administrator), but that was rejected as well.

All attempts to log in give me the same error as follows (translated from Dutch): "This password is incorrect. Please check if you are using the password of your Microsoft-account. U can always reset it on account.live.com/password".

ALL user accounts are able to log in to other machines. None of these accounts are Microsoft accounts, they are either active directory accounts (users and my own) or local accounts (local administrator).

How can I fix this (keeping into account that I am not able to log in to the machine)?

All Windows versions concerned are Windows 10 1809. Upgrading to another Windows version is not an option (we are a hospital and are stuck with this version because this is the latest supported version for all hospital related software by our vendor).

I've tried removing the last Windows updates (going back to September), as well as the new Edge that has been installed today on one of those machines. To no avail, alas.

Thanks for any suggestion!

Jacee said:

You might try talking with Microsoft Support: https://support.microsoft.com/en-us/contactus/

I don't have my Access ID or subscription available, I'm the sysadmin, I'm not the one who maintains our licenses (don't ask).

Besides, I'd rather take my chances asking on forums rather than dealing with MS support, thanks.