CarPlay stopped working with iPhone 13, ios15

Had the same issue. Some have advised to turn off EQ but that didn’t work for me. For those still experiencing the same, I finally fixed it by Resetting Phone.

Go to the “Settings” app > Tap “General” > Find and open tap “Transfer or Reset iPhone”> Tap “Reset” > Lastly tap on “Reset All Settings” > For security reasons, you will be asked to enter the iPhone Passcode. 

This is the other fix going around in the forums which seems to be successful for some people.

THE FIX - Unplug the phone. Go to Settings > Music > EQ and turn one on. I turned on Latin. Then play a song for about a minute on the phone, not on CarPlay. Then, go back to Settings > Music > EQ and turn the EQ off. Plug your phone back in and voila! It should work. via Brutus161.

I have a 2018 Silverado. Bluetooth audio works. CarPlay won’t work at all.

I thought the same but thankfully it was only resetting the phone settings and not necessarily resetting the phone completely to factory.