MP4 FILES WONT DISPLAY IMAGE

Hello,

I have mp4 files from a wedding I filmed. If I click space bar on them or try open them with QuickTime they won't play video(its black) and only plays the sound. If I load them into my final cut pro timeline than I can see the clips. I can't edit a wedding project like this, it will take me forever as I need to separate the clips in to different categories before uploading into Final Cut Pro. Is there a way to fix these files so that I can view them like any other regular video file? Another example is usually when you click on the file to the right it will show some type of preview of the image but instead all my images just show the mp4 gopro player image. It also doesn't work with the gopro player either.