Missing Zoom Window when in a meeting

[MikeFB]

Hi,
I was online in a meeting this morning, using my Mac Mini M1, running Big Sur - latest version. I clicked Full Screen and the Video window completely disappeared. I rebooted my machine, using the most up to date Free Zoom verion I click start, but got now Zoom Window. If I go to settings I can see myself in the settings windo, but I cannot see how to get the meeting room window open again. 
How do I resolve this issue? I do not have a paid account so online chat is not available to me, The Help Chat Bot is unable to resolve this for me.

Can anyone help?
Mike