Mic Works Solo but When Guest Comes onto Call I Can't Hear Guest Until I Unplug my Mic

[Angelnat]

My Audio Technica Mic passes all Zoom tests & works when I hop on Zoom Solo & records (on laptop).

But when a guest comes onto my call, I cannot hear them until I unplug MY MIC. 

I have:

-researched this issue & found NOTHING on this particular problem

- tested on Zoom (it passes)

- asked Zoom bot

- tested & adjusted laptop settings for all the audio/mic things like allowing mic, volume etc etc 

- updated Zoom to latest version

- uninstalled & reinstalled Zoom

- cleared cache

- rebooted computer

Yes, everything is plugged in properly and yes Zoom recognises my mic and is set to it.

NO IDEA why this is happening, I think I also had thiss same issue when I borrowed my son's laptop.

Please help me solve this. Thank you so much.