I tried to test the environment and got the same thing. I replaced my laptop with a desktop computer, but I still see a black screen. All I can do is go to settings.
I also have the same problem today.
The training support in chat said that this an issue with new iso usb
I had exactly the same problem yesterday (2020-12-18) - black screen after "The onboarding process will..." message window. I have tried different network settings, other PC, lowering screen resolution... nothing solved an issue. About three hours before the exam and also few days ago, everything worked fine and successfully went through hardware compatibility test.