BAT VK-52SE - Unity Gain/HT Bypass help

I could use some advice in getting this to function correctly. I have connected balanced interconnects from the processor out to the Aux 2 input on the preamp. I have selected Aux 2 in the programming function and set the unity setting to "fixed" and left the volume at 000 (also tried 001). When I run from the processor (with preamp on, not muted, and Aux 2 selected) I get nothing out of the mains (which work correctly in two channel). Anyone have advice?
Volume readout can be configured to show either db or step. From what you
described, it seems to me it is configured to show steps because you can change
it to 001 (in db mode, the minimum is +- 0.5db). So 000 means the minimum
and therefore no sound. If you change it to db mode and set it to 0 than it means
0db or unity gain.

BTW, in step mode I think 100 is unity gain but I can't be 100% sure because I
don't have the manual with me.
The volume setting on the BAT 52SE still has to be matched to the processor and other sources, so the processor volume control can operate normally, as if the BAT wasn't in the loop. I have my 51SE set at 110 (step mode).
I tried 100 - no joy.
This is strange. Does it work if you don't set Aux 2 to fixed?

Also which processor are you using? Is its output RCA or XLR?
It does not work when set to not fixed. The processor output is connected via XLR. A different preamp (different brand) with a HT bypass works perfectly when connected to the processor. I guess that tells me what I need to know.