How do I play a video cutscene

So ive set the code to:

Con: At the begging of the scene
Act: Play the video of Cutscene1

the video is in cutscene 1 as a .mp4 file and it just wont work. This is really vital to my game and I was wondering if anyone has a soloution.

-Cheers

Try GDevelop Wiki on addin g a video