Thank you for your answer.
I tried mp3 and ogg, no change.
I have a custom theme, so not using the media folder. All the files there are distributed in month folders, in year folders, so it is difficult to find the right file path.
But, I found what was causing the problem. When I tested changing https into http, it works as before. A few months ago I changed everything to SSL, but obviously some values are still the old way.
I can make a dirty conversion by stripping the ‘s’ out of https on the spot, but I would rather find out how to make it work as it should. Puzzling also that it only became a problem months after the conversion.
Is there a problem using the plugin under SSL? Any insights or help in pointing me in the right direction would be appreciated! Even just knowing what to search for!
Kind regards, Mark