Hello,
Thank You for your Patience! We always check out the Live Previews along with the Codes before replying to the Support Queries! What we recommended in Our Replies is to use the mentioned softwares for converting your Videos so that it has the Best Compatibilities. Also, consider using a 1920x1080 Video Resolutions which are more commonly used and accepted.
Additionally, we requested you to correct the HTML Validations Errors which related only to Unclosed Tags, however the rest of the Errors can be ignored since the W3C Validator is completely compatible with HTML5 Markup.
Also, since this is not working for you, please consider finding the code below inside the SEMICOLON.documentOnLoad > init: function() Function Block in the js/functions.js File:
SEMICOLON.widget.html5Video();
and replace it with:
setTimeout( function() { SEMICOLON.widget.html5Video(); }, 700 );
This will definitely work fine. Let us know if we can help you with anything else or if you find any further issues.