Help with retrofit.

[wboard]

Complicated one here, one for the experts.
My 2003 x5 had comms pack as factory fitted option. I bought this vehicle from an insurance company with vandal fire damage. I had to piece in a part of the main loom which put the car back to non nav spec with the big radio plug up front. I then bought retro fit nav loom from bmw and fitted along with all nav components. Nav works fine along with tv although i have no sound output at all. When i try to switch on radio function nothing happens, i get no illumination of the red square by the left hand knob.
I have tested all individual parts of the system in another x5 and they all work so it has to be a wiring issue. Also when i plug in the small radio control unit from a non nav x5 it works the radio function and i get reception.
Any help or ideas of what to try much appreciated.