found a solution
i know - old thead, but after having the same problem yesterday I found a solution.
I´m having 2 mono channels routed to mono outs (1 : Bass 2 : Bassdrum) the mixer section shows only 1 stereo out,bass was left, BD was right. Bad.
Now I went to the environment and switched the stereo out to mono.
Result : only the bass appeared in the mixer, the BD was still audible but no visible channel....bad
Now I assigned BD to out1 and then again back to out2 : in environment now there is a second blank channel (without meter and controls) next to channel 1.
If you switch now between mono and stereo in environment, a second mono channel appears instead of the blank channel.
IMPORTANT : make sure there are no other channels (click, prelisten...) routed to channel 1 and 2 as stereo. check all outputs in environment
otherwise this won´t work.