Recently, for any new projects I create, SD3 does not work, i.e. there is no sound output from the instrument track.  I’m using X1 Producer (X1d build 533).  Interestingly, this problem does not affect my older projects using SD3.  There is clearly MIDI signal exporting from the MIDI data track, but it is not getting processed by the SD3 instrument track (I triple checked its input and output and all signal paths). 
 
Also curious, if I “initialize program” in SD3, then use my MIDI keyboard, I can play and hear drum sounds manually.  But as soon as I send MIDI track data to it, the sound stops and I can’t even manually play drum sounds anymore, unless I “initialize program” again.
 
Suggestions?   Thanks.
 
Greg

Immediately after opening the project:

• Open the Session Drumer3 UI
• Open the VST Plug-in Properties dialog from the VST drop down in the SD3 UI header and
• Select "Do not intercept NRPNs"

Then try playing the track.

Hey haskins02,
 
have you checked if your midi track contains any control change messages?
Same happend to me one time (but it was in Kontakt). As soon as hit the play button to play a midi track, there was no sound, but I could see midi data exporting from the track and receiving in Kontakt, same with my keyboard.
Then I reloaded the instrument and I was able to play again with my keyboard, as long as I didn´t start the playback of my midi track. Later I realised, there was a midi control change message in my track which muted my vst.
 
So take a look at your event list ;-)
 
 

This is my guess too, there is some MIDI data shutting down the sfz engine. This happens occasionally when importing MIDI data.

Thanks.  Your suggestion to go to Event List and remove all controller data both worked and did not work.  Let me explain.  If I copy my MIDI drum track to another Cakewalk project, remove all controller changes to that track, then insert a SD3 instrument track, it works just fine, just as you would expect.  But within the original Cakewalk project, even if I delete all the controller changes on that track, AND all controller changes on all other MIDI tracks/channels too, SD3 still has no sound.  I guess I can solve this problem the long way by copying and pasting all the MIDI tracks (about a dozen) from the original cakewalk project to a new one, but I am still curious why simply removing all controller changes did not do the trick on the original project.  Any further ideas appreciated.  Thanks again.
 
I did not try the suggestion from scook, as I don’t understand how to find the “VST Plug-in properties” from his instructions.  

The short answer is, cleaning up the MIDI tracks should work. Maybe this will help WRT plug-in properties:
 

Thanks for further instructions scook on "Do not intercept NRPNs" but after following them (and restarting SONAR), it still did not work.  I guess I will have to do it the long way and copy individual MIDI tracks to a new project.