If you get error "Error validating access token: The session has been invalidated because the user changed their password or Facebook has changed the session for security reasons." - it means that you clicked on "Disconnect" button in some widget.

The Facebook API is a little bit tricky in this part. When you click on "Disconnect" in the widget editor it disconnects your Facebook profile from the Allforjoomla application. So after that you need to go and connect all the widgets again, because the connection to the API has been changed.

And don't forget to click "Save" button after connecting the widget.