One year now Google Chrome has update it’s video autoplay policy as you can see here .
As part of the above sometimes (or always) videos from cb-slide will not start playing. I quick fix is to patch the header.php file from theme’s root folder.
Open header.php file and search for the video tag “<video”.
Just after the above string you found and before id add “muted autoplay”, without the double quotes.
I Hope this fix will be applied to the next update.