I didn’t put the link but the WordPress Audio page still works in Firefox with mp3 as shown in my first screen shot. https://en.support.wordpress.com/audio/
I’m using Firefox 20.0.1 and the flash player fallback seems to work on en.support.wordpress.com/audio/ but not on my site. Is there a reason for this? Is WordPress.com using a new/different JetPack and Flash player fallback?