Header video not working

Hi ,

I am using Twenty Seventeen (HEB version wordpress – newest version) and i’ve putted a nice video on my site header (media headline video) , it works great on desktop computers but for some reason it doesn’t work on mobile or on tablet ,I’ve also tried to put a youtube link and still – nothing , on mobile & tablet only the site icon and title appears, and even if i take them off , still , no video is shown and it look like a blank header 🙁 – can any one tell me why (when i do “mobile preview on my computer it works , but not on the mobile itself?

My site is : http://www.im-online.co.il if you need to see it yourself.

I need your help with that pleaseeee

Many thanks!!