Iphone won't play in car through USB

My iPhone 14 pro max would play through my car stereo via usb only intermittently. When it worked, it was great, as Siri control permitted selecting music, podcasts, etc, hands-free. A recent software update has killed it again, and I've done a lot and spent a few days deleting, reformatting, etc., with no luck. I think it's the iPhone's "music" app. Podcasts, Siri, and a few other things work, but the music app just won't hook up. An app called "Audio Player" works perfectly in addressing all my playlists, songs, albums, artists, and genres, and will shuffle. Other apps also work. The only drawback, at all, with "Audio Player" is the lack of Siri control. But at least I have my music back. If you share this problem, you too may find it isn't your car, cable, phone, or file format, it's the Music app.