Audio Issues on participant end

Hello - recently my participants can only hear me out of one side of their speakers.  So it's mono on their end not Stereo.  I am being told it only happens when they are zooming with me.  I am running everything through my black lion Revolution audio interface,  all of my settings are selected to run through that interface.  Zoom - and my MacBook Pro.   I am currently running Mac OS Big Sur 11.6.5.  I am using an external mic that is connected through my audio interface.  Everything is connected properly and snuggly plugged in.  I have rebooted a few times to no avail.  Can anyone tell me why this might be happening?  Thank you!!