Appletv setup fails with 71160 error whilst setting up

I am setting up Appletv remotely for my mother, difficult enough as she managed to press the button for french..

That's not the main problem though.

We are setting it up on her ipad mini 2.

We get past the bluetooth handshake, then the ipad asks for her appleid and password.

I don't know why it does that, given that she should be logged into apple on that device.

Anyway, she types all that in, then it goes to setup icloud - seems to do that for a long time, then fails with error code 71160.

I tried to log into icloud with her ID and it took an absolute age - so I did wonder whether it was just timing out.

Any ideas as to how to sort this out?