I don’t think that it’s any file content. I’m not sure if WordPress analyses the file.
I have got files uploading into the media library via the add audio block interface and the media library add files. Those files didn’t appear when I tried to link them to the page.
As you can see from the screenshots above, using the single upload doesn’t work. Using the media library button in the middle allows you to upload a file but doesn’t show files loaded directly into the media library, see the first screenshot.
These were my questions:
I’ve got a workaround but my questions are –
why can’t I do a single upload via the audio block insert?
why doesn’t the library button show files I’ve uploaded when I want to place them on a page but allows me to upload to the library from there?