As long as your computer soundcard has a GM synth onboard you should be able to hear something even if it is not the exactly the same sound as the Kawai. For example you should be able to assign the Kawai piano part to the piano patch on your computer's GM sound set. It is a little odd you heard nothing. Try reassigning the patch in the MIDI file on your computer to see if that starts producing some audio when you play it back.