I just updated to WP 3.6 and was really excited for the ability to natively embed self-hosted video files. But when I tried to do this in my WordPress install it simply gave me a gray box with a link to download the file when I visited the page. I reverted back to the 2012 theme and then up to the 2013 theme and they both supported and properly displayed and played the media file. I have searched in the WP documentation and codex and have not found how to add support for media playback to my theme. Could someone please help me out?