Overlay does not work on a video background

Background Plus effects are applied to the first image and/or video assigned to a section background.

It’s possible that you have BOTH a background image and a background video assigned to a section. If this is the case, then Background Plus will assign the overlay to the background image rather than the video, because that’s the order Divi places them in.

Try removing the background image to leave only the video. BG+ should now apply the overlay to the video!