Problems with Header Media video link to YouTube

Hi there, I seem to be having issues with linking the Header Media to a YouTube link for my website (katchien.com). It worked about three weeks ago however when I checked the website today, it just defaulted to no header at all. I've checked on my mobile, laptop and desktop devices and it is the same problem. When I include both the YouTube link and upload a header image, my website blinks the header image for a split second then defaults to no header with the page starting from Site Identity section. When I hide the header image and just include the YouTube link, it defaults to no header at all. When I delete the link to YouTube and just randomise the uploaded headers, the images work. Could you please advise how to fix this issue? I would very much like to load the video rather than static images in the Header Media area of my website. Many thanks, Kat