https://www.scirra.com/manual/181/video
Maybe you got the compatibility problem
Compatibility
On Safari for iOS and Chrome for Android, video playback cannot begin unless triggered by a user input event. The Play action will work in a user input trigger like On touch start, but if done outside of that it cannot play right away. To work around this the video plugin will wait until the next touch event to start playing the video. This also applies to autoplaying videos: it will not start until the first touch.
Safari on iOS does not currently support rendering video inside the game canvas itself. To work around this, the Video plugin creates a video element floating above the game, similar to a form control. This ensures the video can appear, but prevents other objects being displayed on top of it.