If the MP4 video file that you download is only playing audio, watch this video for an explanation on how to fix the issue or read the steps below.
If you're MP4 video file is playing as audio only, you need to:
- Control+click on the video file
- Select the Get Info option from the menu that opens
- From the Info box that opens, go to the 'File and Extension' box and remove the .m4a extension that is add the end of the name. Making sure the file ends with only .mp4 instead.
- That should fix it.