Did you ever get this sorted? I've found that with my audiofuse studio, I need to do both the ADAT in and out to make sure the device I'm syncing with gets the clock sample rate, otherwise the ADAT doesn't seem to work. This is different than on my older focusrite scarlett that only had one ADAT in and no output.
Edit: Ok, so I've been working with a superstitious behavior - just tried this again with only 1 ADAT cable and it worked fine this time around.....not sure what I did or didn't do previously, but I was also relying on the second cable so I could use the analog outs on the 8pre as well.