You should be able to see the photo taken with your webcam.
If you see it, everything is fine. Your camera and your browser are suitable for the online supervision.
If you only see a black surface, either your browser or the used webcam does not support the online supervision. The reason may be specific settings which you have made or that were made per default.
If you see a grey surface, your browser probably needs a flash plugin. In this case we recommend another browser such as Firefox or Chrome.
If you use Firefox, please allow permanent camera access: