I have been having this problem for a year now, hoping someone would come up with a fix.. It is possible to fix on Nvidia cards!
For some reason, my computer is not capturing window capture - Apparently this is an old issue that could be fixed by going to radeon additional setting and selecting the integrated graphic driver, for running OBS itself. - However, you can't do that in the new Radeon Drivers "Additional setting missing" Or "Moved to Display" But! - When you are not on a computer with a build in graphics card, like a normal PC, then there is no option to do or change anything - You simply can't do window capture.
I have worked out that I can use Display Capture, but why is no one @ AMD addressing this, there is a lot of streamers out there!
I mean I know why, but please do something about it!
So for now, I guess Display capture is fine.
Please bump the subject, if you have the same or similar problem.