Hey, pro, you may be getting to the point that it's time to try omeyhomey's fix.
Mine plays cd-rs just fine, although I have to say that I always record them at slower speeds. Some cd players (not just those in cars) can be finicky about that, so I always go with 6x, 8x or 10x at most.
A couple of times in the past my head unit has failed to recognize the changer, in each case a reset/reboot fixed it and it has been a long time since it has recurred. I'd suggest starting there.
Take care and enjoy the ride,
Greg