How to make all the movies playing all at once upon a click? (KeyNote 6.2.2)

Hello, I made a presentation using KeyNote (don't remember the version) over two years ago. When I tried to play back the presentation, a series of 4 videos in one slide played at once upon a click. That is what I intended. However, on the next page, none of the other 4 videos played. I had to open and save the video files again perhaps due to a different OS being used (the current one is 10.9.5). When I played back this page, upon each click a video was played. How can I make them playing all at once upon only one click? Thanks.