Drivers should not enter into it. Neither Windows nor SONAR has any knowledge of outboard controllers, as they only see the MIDI input to your interface. If a driver was involved, it would have been the one for your audio/MIDI interface. But because you are able to record MIDI, we can assume that Windows knows about the interface and can communicate with it.
From your OP it sounds as though your problem is audio-related rather than MIDI. You can test this assumption by plugging some headphones into the Triton and playing back your track. If you get no sound in the headphones, then the instrument isn't receiving the MIDI you recorded. In that case, verify that you've selected the MIDI device as your output destination, from the dropdown list of Output devices in the track header.
If you hear sound in your headphones, then MIDI's not your problem. The next step is to route the synth's output to an audio track in SONAR. You should be able to record that audio, even if you cannot hear it. To hear it as it's playing back (without recording it first) you need to turn on Input Monitoring. That's a button in the track header.