"Invalid meeting ID"

When I try to test Zoom on my desktop Windows 11 PC, I get this error: 

"Invalid meeting ID  Please check and try again."

To me, that does not make sense, since I'm only visiting this URL (not creating a meeting ID):  https://zoom.us/test

My Zoom version is up to date, since I downloaded & installed it 2 days ago. 

Additional Clue:  It often takes 10 minutes for the Zoom desktop client to open, after I initiate a test. Even though I keep the Zoom desktop app icon in my taskbar.

How do I fix this?