i've been trying to set up my OBS so that i can stream co-op and do some runs, however OBS is failing to capture the game. does anyone in the community know how i can fix this?

One way to do so is monitor capture and then crop it to capture only game layout.

Have you tried both window capture and game capture? I experience this issue when I try one or the other, and most of the time the other works.

If you play solo mode, you can set compatibility with Windows 8 and use "Window capture", but in co-op mode it will cause lags.