USB MODE: I "See" the input Cannot Hear it

Hello. I’ve got audio coming in on several inputs via USB (Source is Reaper). I can see and hear inputs 1/2. I see input 3 LED jumping, however, there is no audio feeding the main bus, and the fader is up.
I’m brand new to this mixer, which I adore, but this has baffled me. Analog inputs all work as expected.

Is channel 3 muted? Is the channel assigned to the L/R fader?

Thx for the reply. Not muted and I’ll check the LR assignment. Analog not a problem. I’m just learning and adoring the board.