Can't play mp4 files (case 37125)

[osuncogdevlab]

I am trying to program a really simple experiment in DirectRT where a short video is played and then participants make a response. I can get avi files to play but for some reason I cannot get my mp4 files (which play in media player) to play in DirectRT. I have attached all of the relevant files and stimuli and have reduced the experiment to a single line in the csv file. Any help would be appreciated. I have tried saving the videos under different resolutions and frame rates and have also changed the bit depth in the colour.text file. No luck. Thanks in advance for your time.