This problem occours when a big update of windows is done, that clears the settings of the Blackmagic device.

As default, the 4 ports are grouped in pairs to be used for dual output.
So this need to be changed in the Blackmagic Desktop Video Setup program that is installed togheter with the drivers from Blackmagic.

1. Start Desktop Video Setup from the Start menu or the control panel.
2. Select the device DeckLink Duo (1) and press the settings icon
   
3. Goto the tab Connectors in the top.
4. Change Connector to SDI 1 from SDI 1 & SDI 2
   
5. Goto the device DeckLink Duo (2).
6. Go inte settings, and tab Connector.
7. Change to Connector SDI3 from SDI 3 & SDI 4
8. Save the settings and restart Sport In The Box.
9. Now all devices should show up in the Video input list.