I was only seeing black until I selected the exact output in the Blackmagic device side of live input.

Yes, you have to match it exactly (it's kind of a pain because there are so many options for the BM devices. By setting the framerate in the Blackmagic software you tell the hardware what to do and when you tell Isadora the framerate in Live Capture you tell Isadora what it's looking for. Thus if you told the Blackmagic device to do one thing and told Isadora to look for a different thing, you get no input (because you told Mx. Blackmagic to put on a red suit and then told Isadora to look for a person in a blue suit).