If you want to use a MP4 video hosted on Google Drive, you will first need to generate a shareable link and then change the URL before using it in FV Player: just replace the open?id= string with uc?export=download&id=.
That means, if you get a generated link, that will look like this - https://drive.google.com/open?id=0B32098YdDwTAcmJxVl9Kc1piT2s, you will need to change it to this - https://drive.google.com/uc?export=download&id=0B32098YdDwTAcmJxVl9Kc1piT2s
Then append #.mp4 at the end of URL to ensure the file is detected as MP4.