Hello there,
This is not a problem of our product. This is a common problem for developers around the world. What would make it work background video on smartphones and in all browsers requires non-standard js tricks.
No to mention, if you google this subject, you will realize the scale of the problem. In addition, the companies Google and Apple have a policy prohibiting autoplay video for all new device models. In any case, use a video background is very bad for page speed load on mobile devices.
The best way is to completely abandon the background video on mobile devices.
Thanks!