USB AUX not working

Hey there, Appleguy0504,

Thanks for visiting the Apple Support Communities. If we understand, your iPhone 12 Pro no longer connects with your car as expected when plugged in via USB. You've come to the right place to get help!

First, check with your car manufacturer to confirm your stereo is compatible with your iPhone model and iOS version (which you can find under Settings > General > About).

If the issue persists, please follow the instructions below on troubleshooting, which can be found in the Apple Support article How to connect your iPhone, iPad, or iPod touch to your car - Apple Support:

"Connect using USB playback

1. Restart your device and your car.
2. Make sure that your device is unlocked and on the Home screen.
3. If possible, try to connect using another cable or USB port. Check the manual that came with your car to learn how to connect an Apple device.
4. Check your charging port for any debris or damage. Make sure that your charging cable is properly inserted into the port.
5. Update your device.
6. Make sure that your stereo is using the latest firmware from the car manufacturer. Check your car's manual for more information.
7. Try playing audio from a different app. If you can't play audio from a third-party app, contact the app developer for help. If you can't play audio from an Apple app, contact Apple Support."

Best!