I have some files I want to protect which are only available on Google Docs/Sheets. When I add a link to that doc/sheet in the URL section of a new download manager download, then I put the shortcode, it does nothing when I click the link.
Another download manager (which I will name in a private reply because I don’t want to advertise other plugins on your forum) has this same problem, but it has an option to redirect to the link instead of forcing the download, which fixes it.
I wonder, is this possible with your plugin? It seems to me like the reason it doesn’t work is it’s expecting a file with an extension, and is setup to use the browser download function. And since it is a direct link to essentially a web page, a browser cannot direct download it.