Headunit help please!!

I've got a 2006 RRS and the headunit display wasn't working so I've bought a secondhand headunit and I've fitted it and it all works fine apart from no sound!!

Checked online and have disconnected the battery and connected the + and - terminals....still not working.

Checked the fuse behind glovebox all OK.

No fuse on the actual headunit.

As soon as I plug old unit in the sound is there.

Any idea's please??

Maybe it needs coding to the car?

have you connected the fiber optic beam wires in there are two one for the satnav and the other is radio sound to the amp

Wonder if going into the hidden settings on the centre screen may help , or maybe the amp has failed ??

see there’s also threads on the RRS forum

https://www.rrsport.co.uk/forum/index.php

also heard if the battery is low it will start turning systems off