Am I the only one to have a very hard time with Cakewalks' software instruments ?
 
First none of the SI instruments worked and there were no .prog for them.
I had to reinstall them in the command center to be able to load a program.
 
Second, I insert a Cakewalk virtual instrument, such as Dimension Pro or SI Guitar, choose a program / preset. Works well I can play notes on my midi keyboard.
 
Then I select a midi track to output it to the virtual instrument and there is no sound anymore.
 
In order to check, I select the VI track and play on the keyboard and no sound.
 
This happens exclusively with cakewalk instruments. It doesn't happen for example with Ivory, Play or Kontakt.
 
This is very very frustrating.
 
On Sonar Platinum x64 latest version.

If you are using a virtual instrument track, you don't need to output to a midi track.  The VI track is a combo track  which includes the midi track (data) and the audio track.  If you can hear the notes played by your keyboard (as you note when you first set it up) you are set up correctly and don't have to do anything else (except hit record).

Thanks for the answer!
 
I'm not outputting to a midi track though, I'm outputing from a midi track.
This makes it much more readable and easier to switch between different virtual instruments for test purposes.
Also like I said this problem occurs exclusively with Cakewalks VI.
 
Anyway, trying your solution, the mere copying of midi notes directly into the VI track is enough to make Dimension Pro silent.

After a little more experimentation, the problem seems to occur - again, exclusivement with Cakewalk's own virtual instruments so far - when there are more than a few VIs.
 
I was successful in a new project with Dimension Pro + Lizards Lounge + Ivory + Play + SI Bass Guitar
 
Adding another Dimension pro resulted in neither working any more.
 
Adding another Play after that did work.

Describe how you are inserting instruments and which options you are choosing

It might be helpful to know the source of the MIDI data too. Was it recording in SONAR or is it an imported file? If imported where did the file come from?

Either Insert / Soft Synth / VST2 / The Soft Synth or from the browser
 
Options:
Create these tracks:
X Simple instrument track
Enable midi output: Unchecked
 

The shortest I have found to demonstrate the problem:
 
1. File / New / Use normal template
2. Insert Midi track
3. Import midi file in midi track. Check that it works (it will probably be output to a microsoft GS wavetable synth, depending on your setup)
4. Insert Dimension Pro, Choose a piano as a program. Check that it works by pressing keys on your midi keyboard
5. Change the output of the midi track to go to the Dimension Pro Track
6. Press play on Sonar's control bar
 
-> Check that you hear nothing when you play - at least that's what's happening to me
-> check that when you select the Dimension Pro track and play on your midi keyboard, nothing is heard
-> Bonus 1: check that changing the program in Dimension pro doesn't make it audible
-> Bonus 2: check that re-outputing the midi track to microsoft GS wavetable synth does work and you hear the notes.
 
Tested on latest version of Sonar Platinum : Everett
 

MIDI routing can be a tricky bugger. I know not what of I speak but thought I would suggest  you check which CHANNEL things are being sent on/to/from/etc.
 
Sometimes just selecting OMNI fixes stuff. Then you can track down what wants to use what channel where and then define things a little better.
 
Just a suggestion. May not solve your problem. Cheers.
 
PS: I'm almost positive this is not your problem considering the amount of VIs in play but also make sure the MIDI clip notes fall within the range of what your synth/intrument presets are expecting. Sometimes certain synths/patches aren't going to read General MIDI the same way as... well a GM synth/patch would so your notes are too low/high. Also there seems to be discrpenacies in MIDI note octave settings between various programs/synths. I personally don't know the low down on all that and have no problems with what I do but... I'm a guitar player.
 
PPS: Listen to scook above all else. He is perpetually correct with his advice.

Imported MIDI files are often the source of trouble in sfz engine synths like DPro. Have a look at the MIDI data in the Event viewer. I suspect you will find data at the beginning of the track before the first note. This data is shutting down the sfz engine. Delete all the data up to the first note and DPro should work Ok. If you prefer use the MIDI Event Filter MFX or Click the VST2 drop down in the plug-in header, click "Plug-in Properties" and enabled "Do not interept NRPNs"