Yamaha sound system won’t play Apple Music when connected to my iPad via USB-C to USB

What specific model of Yamaha sound system is this?

The sound system will not receive an Audio signal over USB from the iPad if that is what you think would happen. It may if set to do so, attempt to read the music contents from the iPad and attempt to play them.

Before anyone can being to help you need to provide the model of the sound system so we can figure out how it is supposed to work.

From what I can see in the user guide, it seems the Yamaha sound system is supposed to be reading thew contents of the iPad (like an iPod) and allowing you to select a track to play.

Have you correctly set the input on the Yamaha to the USB port?

https://www.manualslib.com/manual/1178927/Yamaha-Rx-V871.html?page=59#manual

Outside of that, something may have changed with the iPadOS and the Yamaha sound system can no longer access the iPad directly.