I will try again tonight, I am pretty sure that I did delete and start again twice over. I think the project must have a bug. So, if this does not work I will try some other projects and see if I have any luck.
 

OK, i have another project now where I cannot sidechain, this time I am trying to get a kick drum to duck a bass part but I cannot get it to work, the bass drum signal is not hitting the compressor ( I have tried a the Prochannel Bus Comp, a Sonitus one and a couple of Native Instruments one). Really not sure what to do? 

I have had a lot of trouble with the ProChannel and sidechaining.

RSMCGUITAR, I think I might try it in the effects bin, see if that makes a difference. I am also thinking, looking at your posts it could be because I am using patch points and aux tracks? I will do some experimenting.... 

RSMCGUITAR
I have had a lot of trouble with the ProChannel and sidechaining.

+1  I have as well.
 
To the OP: In situations like yours I typically use a send to a bus / to hear only the delay and not the vocal.
I use to do similar things on analog gear back in the day by patching the FX at the stereo outs (using a send) to a bus.
I know that's little help, my apology's. But maybe I can try to reproduce this on my set up in a little bit, tell you what I got.

Regardless of how you do it, one consideration is to use VST3 plugins.

The only time I had trouble with sidechaining using the ProChannel compressor was when I turned on mono for the compressed channel. It disabled the sidechain. Stereo got it back again. It never made Sonar crash though.

Grum.

Interesting. Would that be by design? I don't know why I shouldn't be able to sidechain a mono signal.

RSMCGUITAR
Interesting. Would that be by design? I don't know why I shouldn't be able to sidechain a mono signal.

I don't understand the concept behind it not working but it did my head in trying to figure what had broken!

Grum.

I'm bumping this to hopefully get an answer. I find this really irritating. Sidechaining should work in the prochannel.

As a side note: do you guys think development on the prochannel is over? There were requests for a more consolidated insert list a couple years ago which has yet to be implemented. The only thing new was those big knobs. Kinda seems forgotten at this point.