I ran as admin and got the same result.
I don't know if it helps, but this has been an ongoing issue. In the past I could just switch scenes or sources and switch back, and it would resolve the issue. Sometimes I would have to I have no idea why. It's why I'm unable to use hotkeys to start/stop because I never know if I'll get the video or black screen. It's a bit frustrating, but at least I could get it to work. Not anymore. I updated to the most recent version, recorded a couple sessions without issue and now, suddenly I'm unable to record at all. I made no changes between recordings to anything on my PC other than continue some off camera gameplay as usual.
This issue only seems to be the case with the "Game Capture" source at the moment. I'm able to record using "Display Capture" as the source, but rather not since it seems to have lower quality for some reason. The only other thing I can think of is that the preview window is black as well. In the past, I would have to Alt+Tab out of the game once it started. That would show the gameplay in the preview and record. If I didn't it would be black screen in preview and recording.