i installed the One-Time File Download Plug-In, but after not working the plug-in developer emailed me the following answer:
Is that something that can be fixed?
yes. We have some issues with the Shortcodes…
Do you have any third-party plugins installed or CUSTOM JS code? Is it possible to deactivate it for a moment to see if the problem remains?
Do you have everything up-to-date?
Wordpress, Plugins, Laytheme?