the media player works if you have used it while on a current firmware and online (psn).
if you have a ps4 that's been formatted and not used online using a firmware that would allow psn sign in then the media player will fail to play videos.
I have a ps4 with a working media player that plays video off usb and dlna (plex) and I have dumped the v350 version and created a fpkg that installs the full v350 media player.
I have been playing around with it off and on in my spare time and I think I know where the issue is and its not the pkg/fpkg but time will tell for that.
right now only some peoples media players will play video files.
pity, wrong or currently there is no solution, for 5.05 for fpkg working mediaplayer ? never wonder if a miracle of solution will come out, because the videos do not want to work in any way.