As a general comment, lots of stuff on modern cars are VIN locked within many a component firmware... it’s sort of an anti-theft measure, sort of a vendor lock-in measure... That’s true for ECU, PCM, BCM and more... So it may be that the DVD player needs your VIN inserted into the DVD player firmware otherwise a security error is shown...
Is the guy that took your $150 an business? If so, and if he said he’d fix the problem, then as he failed to deliver a fix he should provide you a full refund. As he doesn’t want to provide a refund and is fobbing you off, ring
CAV and have a chat to them about your options.
Since you posted on another thread which discussed pulling specific fuses, why not try “ASL automotive 9799 1444” as was suggested to others within that thread? Or is that the guy that took your money?
You could also try talking to ”No Limits Electronics" in Melbourne (from
this post) as they used to fiddle with 2009 Calais DVD players way back when... no idea if they still exist.
Then there is
Envious Customes which seems to know lots and does great electronic mod work on our commodores
Good luck with it.