More pressing of an issue is that, as my account credentials aren't stored locally, tribesnext had to try to retrieve them from the server, but it said it couldn't. I don't really know how to do it, and I'd rather not make a new account (even if I wanted to, it'd be difficult with my bugged interface, and even when I tried it said it didn't work).
As Blakhart said, this is for Server Support.
But, if you are relating to your login of before the actual master servers were shut down (not the new registering process of Tribes Next), then you will need to register a new account.