Why isn't my background video playing on mobile devices?
Splash background videos are visually appealing, but can be complicated to deal with on mobile devices.
By default if you're using a YouTube video background, when your clients view on a mobile device it will fall back to the YouTube thumbnail image. As long as you control the video, you'll want to make sure a thumbnail is set up.
If you have admin rights to the video, you will be able to set or change the thumbnail image via video settings on YouTube's side.
If you have a thumbnail set, but it's not showing, make sure you're using the full YouTube URL. It should look something like https://www.youtube.com/watch?v=f2s-gi1BZ0o with the full youtube.com rather than a shortened URL like https://youtu.be/f2s-gi1BZ0o .