Ensure that you're callback url setup in your Facebook application account is absolutely correct. That means that it's http instead of https and does or doesn't include the 'www', depending on how your site is used.
Right now, when you're connected with your Joomla user, if you connect via Facebook login, you're accounts will be mapped together, which allows modules to 'know' the Joomla user that is connected to the Facebook account, or vice versa. The actual mapping can be seen in the Usermap tab in the backend.
We're also working on a new release that will be out shortly that will help to verify your API settings more easily as well as having more enhanced connectivity features (such as creating Joomla users and logging into the Joomla site via your Facebook account).
Please let me know if there's any other questions I can help answer.
Please help explain the setup
