Having problems activation your iPhone or iPad since upgrading to iOS 9.3? Apple has released a patch just for you.
Apple confirmed the existence of the bug, and also went on to claim that the bug could affect iPhone 5s and earlier and iPad Air and earlier, as well as clarifying why the circumstances under which the problem occurred (which explains why I have been unable to reproduce the issue).
"Updating some iOS devices (iPhone 5s and earlier and iPad Air and earlier) to iOS 9.3 can require entering the Apple ID and password used to set up the device in order to complete the software update. If you can't recall your password or can't sign in, try these steps."