My friend connects to me. 
His phone: Android 10, Model: M1903C3EG
My phone: Android 10, Model: Samsung A50 (SM-A50FM/DS)
In settings of my friend's phone checkbox "Play pc sounds" active but he did not hear any internal sounds in my phone (when I see video or listen to music). 
What I can do and what can do my friend to solve this problem? Maybe need additional data?