I'm triggering SI BASS from a midi track set to omni...

 
You don't actually send in omni, and there is no option to set the output of a MIDI track to Omni. (Setting the MIDI channel to "none" isn't the same thing. That tells SONAR to use the MIDI channel information embedded in the track data.) The "omni" designation applies to the listener (the synth), and means that it responds to all channels.
 
What you want to do is either set the synth to omni mode (assuming SI Bass gives you that option), or set the track output to channel 1 and the synth input to channel 1. Betcha it works then.
 
EDIT:
Or maybe not. I took a look at the instrument and its documentation, and I cannot see any option to specify the MIDI channel. When an instrument does not offer the option of selecting a MIDI channel, you can assume that it's hard-coded either for channel 1 (most likely) or omni mode. Set the track's MIDI channel to 1.

that's all true flipper. Acutally midi track is set to midi channel 1 and still no sound. Tried with different midi tracks and did not work either. As mentioned before it happened to me time ago and found no reason for that

A lot of synths that are not multi-timbral are wired to respond to omni, but transmit on 1.
 
This situation seems like something else, though.
 
SI-Bass DOES run in other hosts.  Have you tried loading it into a different DAW OR VST host?  You can download a free demo of Brainspawn's Forte, which is a performance-based VST host, and you can test out SI-Bass there.  I just tested it on my system, and once you insert it in Forte, clicking on the strings/frets will play notes in SI-Bass.
 
The above is an attempt to isolate where the issue lies.  If SI-Bass works in a different DAW or host, then SI-Bass itself would seem to be fine, and then the issue would appear to be something within Sonar.
 
www.brainspawn.com 
 
Bob Bone
 

What else is in this project?  Have you tried a new Normal project with JUST an audio and midi track for SI-Bass, and of course the plugin loaded into the synth rack?
 
Just trying to simplify as much as possible.
 
Bob Bone
 
 

If its not a MIDI track that you created, then look at the Event List view. Maybe the person who created it pointed it to a different MIDI port or put in a volume control set to 0. 

Actually I was considering in checking both Daveni and Robert suggestions, It's been a matter of time bein a Little busy this morning. I'll be doing it tonight and get back with some results. Thank You all

Did you try my MIDI channel suggestion?  Maybe I'm wrong in this case, but trust me: this has happened to me many times.
 
Also, just because you got the notes from another bass MIDI track does not mean that they are in the right octave.  I have some synths that are two octaves off from each other when it comes to bass.  You might try putting four quarter notes in a measure so that each note plays E in a different octave.  See where the SI normal range is and then see where your track is.
 
If this is imported MIDI, it could be a MIDI channel problem AND an octave problem.

Guess what. Event List and Event Inspector revealed that this midi bass track was routed to midi channel 2 by default. Changed to channel 1 and it works perfectly. Thank you all for your repplies, suggestions and interest. Great forum.

Yay!

Hey guys.Im having very similar problems with si-instruments in sonar 7.They work great stand alone.Ive even recorded a couple songs before with the bass with no issues.
Now I get no sound when I open it in sonar.The only time I can get sound from the bass is when I open the synth options and hit a string on the bass.I try to even click midi out and ok,sound then goes away and box is unchecked for midi out when I return to the options.Very frustrated and running out of ideas :( Any help would be highly appreciated.