Unfortunately, it appears that certain parameters aren't passed to the ad_message_below template hook.
You might notice when using this add-on that the link which is shared does not contain the post number. In fact, the link that is shared doesn't even work properly.
This is because the details of the post ID aren't passed to the URL.
As odd as this sounds, please disable the add-on. This will of course disable the Listener containing the template hook and template create events. It will, however, leave you with the templates that make this add-on work.
To call these templates, edit template ad_message_below and add the following at the bottom: