Video header on mobile

Hello,
Happy new year to everyone here.
I know a lot of people previously asked the question about the video header not showing on mobile phone. I understand it’s because of bandwidth.
I nonetheless tried to create a child theme as seen in another thread : https://www.ads-software.com/support/topic/video-settings-twenty-seventeen-theme/ (with functions.php + style.css) but still, it doesn’t work.
The video, which is hosted on YouTube, does show, but does not play.
Is it because it’s much too large?
Why is it impossible to change this?
What other theme could support the video header on every device? (As a dance company, we’d like to have a moving picture as an intro).
Thanks for your attention!

Password : COLEGRAM20

• This topic was modified 4 years, 10 months ago by nemo79.
• This topic was modified 4 years, 10 months ago by nemo79.

The page I need help with: [log in to see the link]