Will file a bug report, but wanted to post this in case it might help someone else.
I was logging into alpha accounts in order to add to skill queues, and after logging out of one of them, I found that I couldn’t log into any others. Instead, I kept getting the prompt to upgrade to omega. It seems the game thought that I still had an account logged in, and was prompting me to upgrade in order to log in more than one account at a time. A restart didn’t help.
I couldn’t remember what was the last account I had logged in, so, I started all my alpha accounts, and tried logging into each one until I found one that let me log in. I immediately logged back out, hoping that game would now recognize that the account was logged out, and… it worked! I could then log into my other accounts.