I seem to be having the same issue with an apple account I had created. Shortly (within a day) after it was created it became locked with no explanation. I have been told by Apple Support that they are unable to tell me why the account was locked, and have not provided any path forward. Have you made any progress on this? The only think I can think is that my account was flagged because I am using a custom domain for my email address. But its hard to say if that is truly the case.