Hi Derek,
Some things you can try:
1) capturing from another HD-SDI source to see if that works
2) ensuring that the output of the camera matches the format expected by the card, i.e. the presets you’ve used.
3) Check that you’ve not set the SDI output of the camera to down convert, else you’ll be sending SDI but the card will still be expecting HD-SDI.
regards
Kristian Lam
Blackmagic Design