There have been a few cases in which users are somehow able to create an account with no account type. I don't know how they are able to do this, but I have gotten calls from people unable to register for a professional training. I look at their account and see that they do not have an account type, and when I change their account type to professional, they are able to register. See into Powell River account as an example of what I see of the problem in the backend. Are you able to look into it?
Issue #297 closed