It worked perfect when I first got my car last month and since then it has stopped. When I am connect to android auto via usb cable, it will not play. It works flawlessly if I connected by bluetooth. All other music apps work (YouTube and Google Play Music) when connected by USB Cable. So it's not my cable or my car. It will play the music when I press the voice command button for google assistant but shuts off when the google assistant is done.
I have tried uninstalling both Spotify and Android Auto but it still wont work. And I also tried clear caches and allowing all permissions.