video header not showing up on mobile devices

It was easy enough to set the header to a youtube url - however, only appears in the desktop view of the website. Even on the desktop view, it first 'flashes' the original theme header image - and then replaces it with the video. The bigger problem is that it doesn't show the video header on either a phone or a tablet..? Any ideas? Thanks https://catchthemes.com/frequently-asked-questions/#question-customization-10