[Manuel Hernandez-stumpfhauser]

I had the same problem, no sound, no waveform display in after effects and I found my solution.

My clips were captured via component signal with the Matrox MXO2 in Final Cut Pro and it happens that the matrox captures more than 2 tracks of audio. My first 2 tracks had sound in them but the rest didn’t. For some strange reason when I imported these files into AE the software only recognized the tracks without data.

I had to remove the soundless audio tracks from the Final Cut Pro timeline and then reimport the XML generated from Final to After Effects.

This fixed my problem