Some iTunes and App Store users are currently unable to log into their accounts using their Apple IDs, receiving a the following error when attempting to sign in: "FATAL::Unable to process your request. Please try again."
The problem, which seems to have originated last night, is ongoing according to a thread on Apple's online Support Communities and multiple users on MacRumors' forums. The error occurs on both mobile devices and Macs and according to user reports, it is affecting the App Store, the Mac App Store, the iTunes Store, and the iBookstore.
The multipage thread on Apple's support forums suggests that the issue is fairly widespread and there appears to be no fix available at this time. Multiple users have reported the issue to Apple and the company appears to be aware of the problem.
Update: A number of users are reporting that the issue has been fixed and their accounts are now working normally again.
Article Link: Some Users Unable to Log In to App Store Due to 'FATAL' Error [Updated]