Unfortunately, Facebook recently changed how Open Graph Actions work altogether. Previously, you could create completely custom action types, which JFBConnect supported, for things like "Took a course" or "Raced a car" or "Jumped out of an airplane".. any action you wanted to say a user took could work.
With the 2.8 API release last month, they removed the option for custom actions. You can still do their pre-defined actions, which JFBConnect supports as well, but they are more limited. Please take a look at their description page to see if one of the support actions there works for what you're looking to do and we can help provide info on how to create a button to trigger that action:
developers.facebook.com/docs/sharing/opengraph/using-actions
We need to update our instructions a bit because of that change and make modifications to the extension as well. It will take some time though as we need to support backward compatibility for the users who still have custom actions implemented, which are supported through most of next year.
Another option would to simply present the Facebook Share button on the completion page after they're done with your course. That's extremely easy to setup and very familiar to most users, which can help it get more traction.
Thanks,
Alex