Unable to play mp4 files from DS-2CD2123G0-IS

I have managed to set up the camera to record to my nas drive with motion detection. All I can seem to find is one mp4 file that's always 256mb and only part of it plays in VLC until it just stops after a few seconds. I have tried to use the hikvision IVMS 4200 software to play them but it doesn't have an option to actually open a file. How can the files be played properly