Camera disabled on computer with usb web cam, cannot enable. Claims: AUD

Element-desktop 1.7;34 with a local private server. Other computers with built-in cameras work fine. Only the computer with a USB web cam (Logitech C-600, which works just fine with other apps) has this issue. The local network connections are just fine.

Debian 10/stable, up-to-date, with KDE/Plasma.

Description

On startup, the main window pops up and displays the text messages just fine. When I click on the jitsi icon the video field displays "Jitsi Video Conference" and a button to "Join Conference".

When I do that, the blue circle spins for a while and then at the top of the video field it displays $roomName and AUD. The camera icon and the microphone icon have slashes across them and clicking on them does not enable either.

Shortly after (30 seconds), a pop-up says "You have been disconnected, you may want to check the network connection. Reconnecting in 30 seconds." and then it counts down.

When it reconnects, the top field now says "Jitsi Conference Bashful Strange Cheese" and AUD, until it disconnects again. You would think that there is no video, but if you click on the ^ (video settings) next to the camera icon, the camera turns on and a small rectangle with the correct video appears, but it never gets displayed in the main video area. The disconnections happen every 30 seconds, until I leave the video call with the red phone button.

So, it is totally impossible to make video calls from this system and the sequence above is totally repeatable. What can I test or where can I look to find more details to track down this issue? This behavior has been present for a few releases, before that Element-desktop worked correctly on this computer.

Note: the "$roomName" issue happens on all computers, but the lack of video and disconnections only happen on the one with the USB camera.