For the verification purposes, the front-facing camera needs to be running during the whole duration of the test. If you get the black screen instead of the pictures during the initial phase, do not start the test and adjust your computer settings.
You should not see:
How to fix:
1. Check if your camera runs in another application.
2. Check if you have properly allowed access to the camera in your browser address bar:
If it still does not work, try it with another computer or smartphone.