We are aware of an issue with the rendering of the 3DMark application that can lead it to appear black with just the button shown.
If you play on PC, visit https://www.microsoft.com/en-US/download/ and download the Media Feature Pack, after the download is complete and installed go to Settings > Apps > Apps and Features > Optional Features > Add a Feature > Media Feature Pack. Finally, restart your PC.
If you don’t play on PC, please contact Epic Games Player Support.