I don't know the plugin but you might want to give more details of your setup and how you are creating the project. 

karhide
I don't know the plugin but you might want to give more details of your setup and how you are creating the project. 

I do not use surround plugins so I can not comment much on the setup but I am sure there is someone on the forum that can help.  
 
I just looked up the plugin but the website I found was in French so can't really help.

SONAR's support for surround plugins is pretty much non-existent.  None of the Waves surround plugins can be made to work right.  Pretty much anything with more than two channels will have issues.  I've tried a bunch of work arounds but Cakewalk needs to make changes to how the audio routing works, especially with surround buses.  Oddly enough DirectX surround plugins do seem to work correctly but with VSTs it wants to treat it like multiple copies or offers no access to other channels.  It's one area Cakewalk needs to address.
 

Thank you msorrels for your really helpful reply. I hope someone from Cakewalk would see this and address the problem one day…