drumkit playback no sound

Hi, and welcome to this forum. I do not know which SONAR LE you have. If you are using Cakewalk's TTS-1, the drums are on channel 10 by default (on the MIDI track channels output drop down list). If you use another drum synth, maybe try to insert an audio track, and insert the drum synth there (right click and insert desired soft synth, and choose preset / sound in drum synth). Insert a MIDI track, and route the output of that track to your drum synth. Hope it helps.
All the best.

LE sadly does not come with TTs-1, not sure why as it is certainly more useful and better sounds than the 3 included soft synths. Most of LE works the same as ( assuming) X1 as far as menus and midi editing go, but it's not much to get excited about due to the lack of VST's. It's best attribute is as a cheap upgrade path to a new version of even Artist which will blow it away 10 fold.
 
Anyhow follow the help files on inserting and using the VST's.
You need to insert the Drum VST and then point a midi track output at it. LE does not work like the new versions and I don't think it uses instrument tracks which is what your describing. At least the X1 version doesn't, There might be a newer version I'm not sure.
Insert a new MIDI track and put your loops in there see if that works.

What kind of Audio Interface do you have, or do you use the internal soundcard in your pc? Are drivers up to date? What latency settings are you using (while SONAR is open, go to Preferences (P), Audio, Driver Settings and see)? 
 
Maybe try to increase it for playback?
This is on my laptop using MME. Maybe try to switch to WDM/KS or WASAPI? 
Which soft synth are you using to trigger the MIDI track? 
All the best

Yes finally, 
I have selected Si drumkit instead of Microsoft GS wavetable and now it sounds good.
I did't see this selection boxes before I changed audio driver to mme..
 
Anyway, thanks for the help