It seems that this morning Apple has some problems with the recognition of Apple IDs, so if you try to log in to iTunes, it is very possible that you will be greeted by the above message. I don't know when the problem will be solved, but many people also encounter it when logging in from mobile terminals, so if you can't log in to iTunes, you now know that it's all about Apple. I will let you know when the problem is fixed.
UPDATE: In addition to the App Store, iTunes Music Store, etc., iCloud also has the same problems.
UPDATE 2: It seems that the problems have been solved and everything is back to normal.
