why has my account been disabled

The most common reason an account has been disabled in the App Store and iTunes is you've entered the wrong password multiple times. Apple gives you a finite number of chances to enter the correct password before locking you out

TRY THIS:https://support.apple.com/en-us/HT204106

Perhaps this article will help:

If you see a message that says 'Your account has been disabled in the App Store and iTunes' - Apple Support

or

If your Apple ID is locked or disabled - Apple Support