convert midi file to wav?

hi
i don’t remember how i did that but i managed to convert my midifile made from kontakt to wav
in fact it’s exported them to wav and then i could apply my vst effects on the tracks

now i don’t remember how i did that and when i export the tracks with the feature export to audio mixdown then the file is created but there is no sound the wav file is blank

so do you know how to do that?

thanks guyz