Why I Can’t Create New Apple ID In This IPhone ?

Verification Failed "problem connecting to the server" March 2018 - https://discussions.apple.com/thread/8321958 - Needed to connect over wi-fi and not through cellular.

And the opposite:

"Verification Failed, An unknown error occurred" March 2018 - https://discussions.apple.com/message/33184357#message33184357 - "tried again with Wifi off and it worked"