Samsung Galaxy S21 does not show full screen on Zoom meetings.

When I am in a zoom meeting with my Samsung Galaxy S21 it does not fill the rectangle box on the zoom meeting. 

I have been researching and have exhausted my resources. Does anyone know how to fix this or if there even is a fix?

I have tried
turning on HD
Putting my phone on-screen rotate.
When I rotate my phone I STILL get a small image on zoom as shown in my photo

checking settings > display > full screen apps and zoom isn't on there

Called Verizon
uninstalled and installed zoom
I have the latest version
watched youtube videos and searched this community.

I have a presentation soon and would love to get this working.

Much thanks 
LYdia