Paolo,
Can you check and make sure you've entered your Subscription ID into the JFBConnect configuration area? The link you posted should have your subscription ID in it, as that's what our system uses to verify that you have an active subscription.
If that's still not working, you can go to the following link (when Logged In) and download the updated package below. Then, install that like normal:
www.sourcecoast.com/index.php?option=com_ars&view=release&id=13
Hope that helps, but let us know if you run into any other issues!
Alex