Hi--I don't think it's the theme setting that is the problem here. I have the same problem. OBS doesn't seem to be seeing my camera, in my case, but I can stream through YouTube just fine. There are graphic card settings to adjust (plenty of info on that out there and in these forums), but none of them seem to work for me. Everything was fine with OBS, and then windows updated and I get the same as the screen shot above. I'm stumped.