WebMoviePlayer.Play
From Xojo Documentation
Method
Starts playing the movie from its current position.
Notes
By default Safari prevents movies from being automatically played in this manner. The user will instead have to click the play button on the player control itself in order to start playing the movie, which then allows this method to work. Alternatively, the user can change their Safari Preferences (Preferences->Websites) for the web site from "Stop Media with Sound" to "Allow All Auto-Play".