No Ch3 in mixed USB output DDJ-1000

Hi - I'm trying to record using blackhole to Audacity on my Mac from DDJ-1000.  Output from tracks in rekordbox on Ch 1 and 2 are fine and output/record to Audacity fine.  If I try playing vinyl on Ch3, I can hear the mixed master out to my speakers, and see the level on the master, but nothing comes through on Audacity.

What can be happening here?  Thanks.