Challenger Upgrade MMCS

[jenpete]

I have a 2014 Challenger with a MMCS (Radio) (8701A560) with no Sat/Nav. I also have a 2015 MMCS (8750A478) from a Lancer with Sat/Nav.
The wiring of both from my investigations appear to be the same. Minor Earths missing.
I have tried all I know, on the bench and in the Challenger to no avail. The 2015 still works in the wreck it came from.
Is there someone who can help, I presume I am missing something simple and don't mind being embarrassed.
Thanks