This could be a rare one but it is one of the reasons you can face this issue.

Overclocking: Overclocking has known to have conflicts with software.

Conflicting software: If you’re running another capture software on your machine, OBS won’t be able to capture anything, resulting in a black screen.

Compatibility issues: Compatibility issues between OBS and Windows can also cause black screens.If you’re running the wrong version, you’re most likely see a black screen.

Conflicts between application versions: OBS installs two versions of itself, one for 32-bit machines and the other for 64-bit machines.Admin privileges: Since OBS captures your entire screen, it’s very possible that your computer might restrict the program’s access.GPU conflict: If you’re running OBS using one GPU and the application you’re trying to capture on the other, you’ll end up with a black screen inside of OBS.There are a number of reasons why OBS might show a black screen, the most common one being GPU conflicts between the dedicated and integrated GPUs. Also read: How to record with OBS? Where are OBS recordings saved?

Obs black screen windows 10