iphone setup looping at update required to sign in

Setting up iphone SE which I have taken over from my wife. It was up to date last month. Reset to factory condition I get a message saying "software update to latest IoS required to sign in. This can be done in settings after setting up the iphone". I press the "OK" acknowledgement and am taken back to the icloud sign in screen. HOw do I get of this loop? I have seen some references to forced update by short press one each of up and down keys then long press on side key, but the only side key is the silent mode switch which doesn't press.

If I try to sign in using my wife's account (username and password) it behaves differently, sending a verification code to her NEW phone. Why is it behaving differently for the two accounts and how do I get it to log in to my own account?