My friend's iPhone plays music, YouTube, etc just fine through my car's stereo using the USB cable. But my iPhone won't. I have reset and restored my phone. Even after I got a new iPhone it still doesn't play. Why would that be?
Download a song through iTunes. That is all I had to do. Apparently my car's stereo won't play any audio from any app unless I have at least one song in my iTunes library. I listen to everything through streaming services like Spotify so I didn't think I needed a song in my iTunes library.