I've added the nutcracker jaw behavior to a character and it works fine using the camera but after disarming the camera and microphone, dragging a WAV file into my timeline, selecting the puppet, and then choosing "Compute lip sync with audio file" the jaw does not move. I can see in the timeline that the lip sync worked, but no jaw movement on playback. I've tried it with demo puppets downloaded from this site as well and can't get it to work with those either.
There is a workaround -- I turn off the camera, leave the mic turned on, and play my audio file on my pc. Then, with the audio preference set to hear my system sound, the puppet jaw behavior works.