Mobile Fallback image not working. Really need help.

I am using 7.1. I have a video as a background but I would like to use a static image for those landing on my page using a mobile device. I set a fallback image but it isn't working. When I go to the website on a mobile device, it is just the video playing in the background and not the mobile fallback. 

Should I try to downgrade to 7.0 and use a theme? The goal is to have the video playing for desktop users and a static image for mobile. I am open to all suggestions because I really need some help here. Thanks

Hi,

If you share link to page where you use video background, we can give some code to hide video, show image only on mobile