Invalid old Apple ID blocks my iPAD iCloud
I went through the Apple support routine, but they were not able to help me: old iPAD, model A1430, iOS 9.3.6, was linked to Apple ID that was an email address that disappeared. I cannot upgrade the device or do anything, the Apple ID is no longer valid. Not even a complete reset, which also asks for the password of the old Apple ID. All I want is to change that ID to my current ID which I use on all my other devices. Any bright ideas?