Audio issues with musical instruments

I have been teaching piano/keyboard lesson using Zoom, as well as given many lectures for Yamaha using my digital piano. Last Wednesday and Thursday I was unable to hear my students instruments, and they were unable to hear mine. I would hear about 4 notes, then everything was gone. I could hear them speaking perfectly, but no instruments. I use a Windows 10 computer, and all students were on iOS devices. I pay extra for this service, and don't use the free service. What has changed, and what do I need to do to be able to teach successfully again? This is a real problem. Thank you! Lori