oEmbed audio MP3 embed not working

Having a very weird issue getting audio MP3 (served from Amazon AWS) embeds to work on my site. If I put the address of the audio on it’s own line (like all other media embeds), in the admin, I get a message that says

Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled in your browser.

I also get an error in the console that says:

Uncaught ReferenceError: AudioPlayer is not defined

When I view the published page, I get a player button (that doesn’t look like the normal audio player), but upon selecting play, it just says “file not found” and in the console, I get a 404 error for http://mydomain.com/audio/

Other oEmbeds work fine (YouTube, Vimeo, etc). It’s just the MP3 audio.

I’ve deactivated all plugins (no caching plugins), reverted to the TwentyFifteen theme and reinstalled core wordpress files. It works on other sites that I’ve tested on, running the same version of WP in the same multisite environment. I’ve tried pulling files from two separate AWS accounts and from the site directly. Does anybody know what might be going on here??? I’ve never had this happen before. Page for reference:

http://test.stellaorange.com/sample-page/

Any help provided would be much appreciated.