I see in all the screen shots that there is a play option in the menu bar at the top. I don't have one in my window. I suspect that this option is to play a linked mp4 or something, or is it for some other link?
It will play the first movie linked to that DVD. You can put the play button there by choosing customise toolbar from then menu or from ctrl-clicking the toolbar, then drag and drop. Also option-P will play the first movie linked.
