Can't log into app store account
Way back when, I set up my iTunes account with "username". Then iCloud comes along, but requires an email. So I set up "username@mac.com". Not a problem having separate iCloud and App Store accounts, but recently I tried to log into the "username" account, and I get directed to a page that wants me to change the Apple ID to an email, and suggests "username@mac.com". Then I get an error "You can only add the @mac.com address that is already on file in your account.", and I cannot log in.
Please help.
