Reversing Camera Issue

When I road tested my TT prior to purchase, the reverse camera worked fine. The car is fitted with an Xtrons head unit which tbh I am at a bit of a loss to get my old head around, it has so many features that it confuses me. 🙂 Easily done with computers as I'm in my sixties now.

All I get now when I select reverse, is a black screen with a yellow warning triangle which has an exclaimation mark in it. 😕

My two lads who are both into computers in a big way have both tried to get the camera working to no avail.

I think I might have simply switched something off which should be on when I was having a play with it, ok, trying to set up the functions I want, lol. But, without an owners manual I've no way to tell where I've went wrong, so, any ideas anyone?