Zoom version 6.5.9 on Mac is showing black rectangles when screen sharing

I have two Macs, (Mini M3 and Macbook Air M4), both running latest OS and latest Zoom Workplace versions. On both of them when I screen share, my viewers see only the black rectangle (which I also see in the little view window that appears near the controls).  I have similar hardware with the same OS but an older version of Zoom that works fine.  Of course, I suspect the new Zoom version.  We also have some cybersecurity software running on these machines so this is another suspect. 

Anyone else seeing this or have any suggestions?

Thanks,
Rob