Zoom mutes me when other people talk

When on Zoom the other people cannot hear me if they are talking. It is as if my audio feed is subordinate to everyone else's.  Multiple people can talk at the same time and be heard, but not me. I can only be heard if I am the only person talking but as soon as someone else starts talking my audio stops. I can hear them but they can't hear me. Also, my Zoom frame/box almost never lights up.

I have the latest version of Zoom on a 2019 iMac using the internal mic. How can I stop this, so I can talk over people in the same way they can?