converted to midi, then wrong instruments

After creating a song on Muse score 4 with drums , percussion , violins and lead and bass quitar, I exported it to a midi file to play it on a keyboard. When I played it back on the keyboard , some of the instruments like the lead guitar and piano are played back as strings or not the same instruments as on Muse score.I have tried to change channels on the various instruments, but after converting from mscx to midi , still different instrument on the keyboard. Please help. What do I do wrong?