Recording a Black Screen
If a black screen is being recorded by VBOX Sim, there a number of steps that can be taken to try and rectify the issue.
An external capture card has most likely been detected as a new screen. Check display settings and set it to duplicate the centre screen, screen1.
Check the screen resolution, an external capture card may only record up to 1080p at 30 fps.
If using an external capture card, ensure it has been selected from the External Device menu.
Restart the computer.