Audio error: Could not start audio source

Hi,

this is a Raspi3 B and I want to join jitsi meet.

I installed the recent default NOOBS OS.
The camera is a Logitech HD Webcam C525 with Mono-Microfone.

Using Chromium I’m calling meet.jit.si/Name

Camera and microfon are set ALLOW

Thereafter I see the camera picture and an error message:

Audio error: Could not start audio source

What could be the problem?

Thanks for hintzs and comments
Wolf