Make sure the student also downloads and uses the Zoom app.
You cannot use Original Sound for Musicians settings in the web browser.

Sound settings:  In the app, you’ll see a lot of options at the bottom.  On a Windows computer, where it says “Mute” on the bottom left, click on the little carat next to that for Audio settings.  On a Mac, click on “Settings” near the bottom right, and select Audio in the sidepane that pops up.  (Again, these are instructions for the Zoom App!!  This will not work if the student is using Zoom in his web brower.)

Audio
Under Microphone settings, look for Original Sound for Musicians; select all three of these options.

Both Student and Teacher should make sure the Original Sound for Musicians settings are on!