In reply to Paul Diat.

Hi Paul,
sorry for the great delay in my response but your comment was trapped in the spam filter and Wordpress thought it was a great idea not to notify me.
Anyway, from what I can tell you've encountered a common issue I often face myself: some channels don't get the audio even if volumes and routing are ok. I think it's a Soundflower-related issue, and most of the time it solves itself by toggling the mute checkmark of the output tab of a Soundflower instance a few times in MIDI audio settings.

Let me know if that solves it for you.
Luca