Program glitch with slide styles on mp4 video

I posted a few days ago about an audio problem I was experiencing with an mp4 file. "Cannot adjust soundtrack to fade volume on video file". With the help of Jennifer Clark I was able to do some trouble-shooting. After I inserted the video into the show, the audio played fine. Once I added the soundtrack there was no sound on the video file. I finally figured out that with a style that had duplicate layers of the video file, there was no option in layer settings for Video Sound Settings. Even when there are not duplicate layers of the video file, any time there are layers of any type - at least that I have found so far - and I've tried quite a number of them, there is no option for Video Sound Settings in the layers tab. So right now, there seems to be no way to add a style to a video file if one wants to listen to the audio on that mp4. Can you assist please.