Music student's audio being suppressed

My piano student's piano sound is being suppressed during meetings. He says he hears my piano sound fine. I have "original sound for musicians" turned on. Does he have a similar option somewhere on his settings?

He is using an Android phone and I'm on my laptop using windows 11.  

I've had similar problems with other students but they were able to adjust audio settings on their phones. How can I instruct him to adjust his Zoom Meeting audio settings. He claims he can't find anything.

Thanks