rgc
Hi,
Have you made sure that you have the right input and video format selected? If these are not selected correctly you will get no picture in any capture application.
The input is set under System Preferences->Blackmagic->Set Input. In this case this needs to be set to SDI.
Then Media Express must be told which video format it needs to capture, you can change this in Media Express->Preferences->Project Video Format. This must match the format being output from your video source.
If you still have problems, please do get in contact with support in your region as they will be able to help troubleshoot the issue. You can find the support numbers on this page.