That would be why the email is in use. There have been past support threads with this problem of the email not clearing out after termination. Here are the options:
1. Create an account with a different email address.
2. Wait for an account manager to see this thread. They'll either clear out the email from the system, or manually create your account for you. Keep in mind that it may take sometime with their attention focused on all of these updates for option #2 to get done.