Header video not working

Hello - I have created multiple sites using the free My Music Band theme, all of which have featured soundless video headers on the front page - but for some reason, I can't get this one particular website to play the video. hollygash.com I have seen numerous questions about this throughout the help forum, all of which have ended with someone saying that they're responding directly via email, but they don't say anything about how to fix it. I have also installed the Header Enhancement plugin, which hasn't fixed the issue. I have also "Enabled" the header settings on the theme. The video is under 8mb. Can someone please let me know what I'm doing wrong?