Sermon cannot be played

I have added a sermon in a plugin to an article, but even though the play display is visible, it is not possible to play the sermon. All the sermons in the table can be played, but not the one in the plugin.
Link to the site: koebenhavnsfrikirke.dk/hvem-er-vi/vidnesbyrd/malene-toldam
What is wrong?

The player tries to load the file koebenhavnsfrikirke.dk/images/mediacenter/malene_toldam.mp3 , but that one can't be accessed for some reason.
Most likely it doesn't exist, the folder is read protected or there is some SEF extension / rewrite rule in effect.

Thanks. I have to look deeper into the file.

Maybe I have linked the file in a wrong way when I added the page to the menu. However, it is a bit difficult for me to see/guess which item to select (see attached image). Almost all fields are like that i Sermon Speaker.
Can you tell me which one is the correct link?

They should all be translated. It's strange that they are not. Are you using the english language?
The menu item itself doesn't matter however. I've talked about the file itself which isn't accessible. The link to the file needs to work completely independant from Joomla or any menu items. It's a direct access to the webserver which he has to able to answer. If you have set up any .htaccess rules preventing access to that folder or have 3rd party SEF extensions, then that could be the reason that it fails. Or the folder/files have wrong access permissions. It needs to be 644 for folders and 755 for files.

Not good! After chanching the file permission to 644 and 755 the site has crashed with a 403 error - both in frontend and backend, and nothing seems to help solving it!