You must use uncompressed Wav files 44,1kHz stereo to display the waveform! Other files will not display it. Also it is not recommended to use mp3 for creating the show. It is not synchronized properly(e.g. when you set effect time in the show and hear the music, when you play the music from the beginning, the effect will be moved). It’s because of playing mp3 in windows …
Michal