This is a great forum you have here.
Two days ago (September 15th) both my Moto Z and my wife's Moto Z Force lost their ability to launch Android Auto in either one of our AA equipped cars (a Ford Sync system and Cadillac CUE system).
We have been using AA for the better part of a year without major issue.
Here is my description of the issue:
When I plug the phone in via USB-C cable, normally it launches AA and hands over control to the car's infotainment system. However, since September 15th, AA will not launch and both cars cannot see the device.
I didn't find the right solution from the Internet.