Hi Taff,
How did you connect audio between the SDR and the D8B? What I/O cards are installed on the D8B?
Since the SDR has 3 pairs of ADAT I/O, as well as 3x8 channels of analog audio on DB25 connectors, you'd have to interconnect the SDR and D8B using either of those.
Unfortunately, DB25 connectors are used for a variety of formats on different cards for the D8B, that aren't compatible with each other. Cards in the D8B may have analog I/O on DB25, or TDIF (8-channels in digital Tascam format) on DB25, or AES/EBU on DB25.
To make it even more confusing, one type of card even has ADAT optical AND DB25 connectors on it. That's the DIO-8. If you happen to have these kinds of cards installed, then you'll have to use the ADAT optical connectors. The DB25 connectors on the DIO-8 cards are the digital Tascam format (not the 8-channel analog format as used on the SDR for DB25).
If that's all connected right (and the sync set up correctly, as you said you did), then it's probably a routing issue from the D8B. Did you route each of the channels "to tape" for the same channel number? So, hit the "Route to Tape" button in the "Assignments" section so it lights up. Then select channel 1 - push the "Assign" button for it. Select channel 2 - push the "Assign" button for it... repeat 22 times for the remaining channels.
Once that's done, and the connections are right, I think the SDR should see audio coming in from the D8B (at least if record-enabled - not sure if that's necessary on those. I don't have an SDR).
My desk isn't on right now, so I'm not 100% sure if that's the exact workflow... but it should go something like that
Best of luck!