OBS not detecting my camera

I've been trying to connect a Black Magic Pocket Design 4k camera through HDMI to a capture card and running OBS but I'm not getting an image.
OBS does recognize the capture card as I get rainbow bars, but it won't connect my camera.
I'm new to this so I'm not sure if there's any output settings I have to tinker with in the camera or what else could be the problem.
I'm trying to set it up for livestreaming with a capture card and OBS on an up-to-date Macbook Pro.​
Please help, it's for work.
 
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