I bought a cheapo backup camera off eBay for my z120bt. I have it hooked up right now and it won't flip to the backup camera when I put it in reverse. I can switch to it via the menu and it works fine. I do have the reverse line connected correctly because when I do drive in reverse my GPS knows I'm in reverse. I also used an ignition 12v for the camera power from under the dash. If I switch the polarity to ground it goes straight to the backup camera when I start my car. Any ideas?

I have an "X" model but I would guess the camera attachment is similar? I found with mine that the camera needed to have the power supply hooked to the power to a backup light and the ground side to a separate ground or it did not work right. It did not work right with power supplied any other way and it also did not work connected across the two wires to/from the backup light as it needed a ground! I would suggest trying that hookup to see if it works and then experiment with other ways?

Not trying to be a smartass - but did you turn the feature on in setup?