I have the same problem (as have many others it seems) and no matter which email address or iPhone number I try, I get the same message that the Apple ID is not registered.
There seem to be lots of problems with iCloud and Apple ID.
My work iPhone 6 was just updated to 11.2.2 and now I get a message in Settings that I need to sign in again but when I click 'Continue' and enter the password nothing happens. The screen returns to the 'Update Apple ID Settings' with the 'Continue' button again.
On my personal iPhone 6, I did a reset & restore from iCloud and now the software update window in Settings says I will be able to update to 11.2.2 when the iCloud restore has finished (but there is nothing left to finish).