Really strange problem. I checked all routing and everything is showing up but no sound out of that track. 1st track sounds fine and music is showing up in the meters and echo is on. Same project plays fine in my M-Audio interface. Any ideas ? TIA
 
Bule

Are you referring to a mono track or a stereo track? How is your routing setup from input all the way through output?
 

It's a stereo  track. The inputs are routed to the Presonus input buss and the master out is routed to the post master modules and going to the Presonus also and both are showing in the dropdown of each device.

Make sure the "Interleave" button is set to "Stereo"

Just a thought

Make sure that the Stereo input/outputs are selected as there are left/right/stereo choices...

 Where is the interleave ? Heres a screenshot let me know if you see anything !

Track interleave is in the inspector just above "E" in this illustration from http://www.cakewalk.com/Documentation/default.aspx?Doc=SONAR%20X3&Lang=EN&Req=Inspectors.3.html#1224480

Changing interfaces can cause all sorts of input/output routing changes happening. In my case my master out will change to SPDIF. 
This is not an input issue so check your outputs. 
Make sure the track output is set to your master bus. 
There is a way to globally set all tracks to master , see the "track" in the menu at the very top of scooks screen shot. 

Ok thanks I'll try those things and get back. I loaded another song with 13 tracks and iy didn't play 9 & 10 which was also strange. I'll report back.

I use a StudioLive 24.4.2 which uses the firestudio driver... One thing that irks me is that the stereo/2 track outputs are listed last, so they are not picked up automatically.... ever... I must manually set the output to them. (Though I have it set in my templates)...
 
So look to see where each track and mater outputs are assigned and verify that they are pointed to the pair that you have connected for monitoring...
 
Keni