Video do not play on mobile mode

Dear Kharis

Thank you for great theme!!! Please I need your help with this (I did research but the question is not answer there)

I used Video header on my website. When I visit the site on a mobile, I encounter with several cases depend on mobile’s resolution and its OS. for example when I browse my website on an Android mobile, in some cases I could see the play button and so I tap on it to play the video. but in some cases I could not see the playback controls and the video did not play too. I refresh the browsers several times but the result is the same.
I have the following questions:
1- how can I force the video to play on any device like mobiles and tablets?
2- if there is no any way to force the video to play, how we can specify that show an image instead of a video when the device is a mobile?

I really appreciate your help.
Thank you!