It has to do with routing and be sure BB can see the synths to start with. I've never used third party synths in BB. I played with it to see if it could be done and if I recall, at least to me, it was too much effort to get it done.

I prefer to do my synths in Sonar in the mixing stages of the project.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.