Usually this behavior happens when you’re linking to a file in the files folder and it’s not actually there. As in, in this case, the .mp3 would not be present in the files/original folder, so it wouldn’t work from the admin side either.
When I tried to access the mp3 file in any record of ours, I got a 404 like this:
/omeka/files/original/0b73b5483b2c10799342224d073f8018.mp3 is not a valid URL.
I examined the /omeka/files/original folder, and there are no mp3 files in that folder any more. It seems that we need to remove the outdated mp3 references to files that don’t exist.
Thanks for helping us identify the problem. We can close this ticket.