Slack WEbcam not working?

I would like to talk to a friend about Slack, only the problem is that my webcam is marked as from my laptop but nothing is transmitted. I have already looked into the Windows settings under "Data protection settings for the webcam". Slack is not shown there at all. What can I do to make the webcam work? By the way, I tested the camera and it works!

Look here:
https://slack.com/intl/de-de/help/articles/208492868-Apps-f%C3%BCr-Audio-Video-und-Bildschirmfreigabe