Audition plays back thru Sound Devices USBPre 2, but why no input signal?

I figured it out. I'm running two mics into the USBPre 2, the first (left) is powered by the USBPre 2 and the 2nd mic (right) is powered by its own transformer.

I noticed that in multi-track I could arm only one side to record, left or right.

And then it hit me, in edit mode Audition defaults to the left channel in terms ofthe input.  I was testing this using mic 2 (right channel) and thus Audition coudn't hear it. Like many analog boards, Auditon distributes left to mono. This wasn't a software issue, per se, after all. It would have happened on a typical mixer and the advantage there is one would see where cables were plugged in--a nice prompt helping to solve it. A virtual connection can make it seem a bit more of a riddle.

Just to see I went to channel mapping and changed the left channel to USBPre 2 Front Right. Yup. It worked.

Since the mic currently in channel 2 will be primary I'll switch them so that it will be in channel 1 and the phantom powered, less used mic, will be in in channel 2.

Lesson learned. Hopefully this will help with one possible trouble shooting idea for anyone not able to get sound recording from a USB device: if it's a multi-channel device, make sure the primary audio is being fed through channel 1.