Focus Rite doesn't fully function with Zoom

First timer … searched Focus Rite, but the results padlocked on the camera function of Zoom.

I have a Focus Rite Scarlet Solo device.  It takes an external Shure Microphone with the “XLR” connection and my bass guitar in the standard 1/4’ audio jack … digitizes and sends to the computer with USB.  The device works fine on Apples “Garage Band.”  It will discern for the vocal track the mic, and for the bass track, the “instrument.”  However,  when I try to use this device in a Zoom session with my bass instructor, he can hear my voice, but he can’t hear my bass guitar.  Seems to me, it’d be “all or nothing” … 

I DID discover yesterday, in starting my own session, I could hear my bass … but when I joined the session my instructor started … no bass.

what do I need to do in Zoom to avail the bass guitar to the program so that my zoom participant can hear it?

Version 6.7.7 Zoom software.  Thank you for helping a newb!