The first thing I did when troubleshooting was to make sure that the full address to the .mp3 file was being used, and that didn’t make the difference. I’m using a pretty heavily customized version of Standard Theme (https://standardtheme.com) but I didn’t modify the post templates at all. I tried switching to the original unmodified theme, and even tried it in the Twenty Eleven default theme… the player still doesn’t show up. You can see the test site I’m working on here https://69.195.124.84/~cornesj2/sermons/
I’ve found a (hopefully) temporary fix by using the [audio] shortcode available through Jetpack, but it would be really nice if the player would show up automatically. My clients aren’t particularly tech-savvy and if I can avoid having to explain shortcodes to them that would be awesome! I didn’t use the shortcode in the top-most post, so you can see what that looks like.
If you’d be willing to take a look at my WordPress dashboard I’d be happy to give you login credentials, but I realize that that’s kind of asking you to go above and beyond in your support. But if you are interested in checking it out, you can contact me at [email protected].