Using a powershell script, I made a gang of user accounts for some students. Their user logon names were too long for some of them following this format (firstname.lastname.XXXX) - you can see how this could be longer than 20 characters for some people with long names.
This wasn't an issue at all for some years, as we never wanted them to log in to domain machines. We only needed them to have email addresses on our On-Prem Exchange Server (2016).
However, we were recently directed to install GoGuardian on these machines as we had too many students and not enough Chromebooks. So I set everything up for that, but forgot about the long names.
Today I got hit with a slurry of students that couldn't log in to the domain-joined computer labs, so starting with the first student, I renamed his user logon name to something under 20 characters.
Each logon attempt is met with "the password or username is not correct". I've reset the password on the user twice for good measure, and carefully typed the username in.
Event viewer on the DC shows Event 4768. I could not find any other Event ID's associated with this student's login, and I'm trying to figure out what is going on here.
I've double-checked Group Policy to ensure I didn't accidentally apply a policy to prevent anything, but shorter named students are able to log in just fine and all users share the same OU. All computers are in the same OU as each other as well.
I can login to OWA with the same credentials that won't work for domain login.
No worries, it happens to the best of us, no judgement from me ;)