ICloud appears to be disabled for many people right now, based on complaints from MacRumors readers and Twitter users.
iCloud Down for Many Users, Causing ‘The Application You Have Selected Does Not Exist’ Error
Initially, the Apple System page did not show an error when starting problems, but was updated to follow up on a communication issue with iCloud account. The support site indicates that some users may not be able to log into their iCloud accounts and may also not be able to access iCloud web apps and iCloud mail.
Some users see a message about the need to verify their iCloud accounts and when they try to sign in, an error message appears stating that “The application you specified does not exist.” Other iCloud-based services like Apple Pay do not work properly and application-specific passwords fail.
There is no word on when to fix the “iCloud will” issue, but we will update this article when Apple fixes it.