I logged into Server 2012 on our domain with my administrator account through a remote desktop connection. I locked the computer to do some other things and now when I try to log back in it tells me I need to be added to Remote Desktop Users to log back in. This is odd because I was just logged in, I check AD and I indeed am in the RDU group. I remove myself and re-add myself, still can't log in. I delete and recreate my account with all the necessary permissions, still can't log in. I even tried the builtin domain admin account, that can't log in either, same message.
What is happening and how do I get back into the machine??
Perhaps the domain administrator made changes to the domain's group policy such that when you attempted to log in again, your session was loaded with the a new group policy that restricted access unless you're in the Remote Desktop users group. Or you may have been removed from the Remote Desktop users group.
To remedy the situation, I will ask for the credentials for the local administrator account and log in to the machine using those credentials. Instead of logging in with the domain, I will key in BUILTIN\administrator (usually, that is the default name of the local administrator account) and log in accordingly with the requested credentials.