Stuck on setting up Apple ID

I work in a phone shop, so we do a lot of data transfer for customers. From time to time we'd get an issue where we are stuck on the "setting up Apple ID" screen.

Normally restarting the process fixes things but once in a while, nothing helps.

Today this happened again. Took us 15 resets to get it working.

We tried:

- restarting both phones

- checking for any T&Cs to be agreed on (none were needed)

- set up the phone with no ID

- set up the phone with the ID but no data

- try public store WiFi

- try private hidden store WiFi

- try hospot

- try data

- check software update if maybe there's T&Cs there to be accepted

- waited 10 minutes on the screen

None of these worked.

In the end these are all the steps I did before trying one more time

- stopped icloud back up on the old phone (rather at that point it had completed) (I think this is what fixed it)

- went to Apple account online and added gender (perhaps its any change of settings, but it could also only be gender issue, doubt though)

- download Apple support app (maybe any app works as long as it authenticated the person, maybe it has to be AS) (wanted to see if there's anything I can do on there to fix it, such as accepting T&Cs, there wasnt)

In the end something fixed it and it worked.

The new phone was a 15 Pro with 2x the storage of the old, 14. Pro was on newest software, 14 was on 17.4.1 as there wasn't enough storage to download and update phone.

When I say 15 attempts, I mean 15. Could be more, I don't even know at this point. Took me 2 hours.

[Edited by Moderator]