Your Apple ID has been disabled message when in iTunes Store

Try resetting its password (and then logging out and back in everywhere) : If your Apple ID has been locked - Apple Support

If that doesn't fix it contact iTunes Support and see if they can/will re-enable it : http://www.apple.com/support/itunes/ww or https://www.apple.com/emea/support/itunes/contact.html

Your Apple ID becomes disabled for one of two reasons:

1. You use the wrong password or wrong security answers too many times

or

2. You owe the iTunes Store money or your iTunes account has an issue that needs to be fixed.

If it's 1. , you can get started fixing it at https://iforgot.apple.com

If it's 2. , you can get assistance at iTunes Store - Contact Us - Apple Support