No video from capture card or webcam?

Trying to set up Composure for a mixed reality project with the camera feed coming in through an Elgato Game Capture card following this documentation but I’m literally stuck at step 1: Playing Live Video Captures | Unreal Engine Documentation

I can select the card as a capture device but nothing shows up, and other programs confirm the feed from the card is being viewed. I thought it might be a compatibility issue but some googling seems to confirm at least a few have got the same card to work somehow. Even after restarts I had no luck getting a feed, so I decided to try doing the same on my home computer (so a different system) but with a USB webcam, same thing here, I can select it in the dropdown, but nothing appears.

Is the documentation outdated or am I doing something wrong?

Did you ever get an answer here? I’m having the exact same issue. I’m not getting any input from my Magewell capture card. It works elsewhere, but not in UE 4.27 preview 4.

No answer, doesn’t work on any of my three machines, works in the UE5 Early Access though, but the vive tracker refuses to work with UE5 so I’ve given it up for now until there’s a reasonable indie tracking solution.