My iPad users cannot play their violin for me, it cancels out the sound

[FiddleSchool]

Hi,

I'm a fiddle instructor and I host many Zoom classes. A new problem has come about recently that we've never encountered. It seems that when users are on a phone or iPad, I can hear them talk, but as soon as they play it cancels out the sound. Can this be remedied? Surely it can. 

Thanks,

Katie