Can you go into your project on
cloud.google.com/console and go into the "Data Access" menu section? Please tell me what scopes are listed on the page.
Also, on the page that is coming up, what is the value in the email input field? If the email field is not showing, make sure "Email Field on Registration" is enabled (from JFBConnect > Configuration > General > Show). When JFBConnect is unable to fetch the email address, the user will be directed to this login / register page even if automatic registration is enabled. If the email field is blank, that'll tell us a lot.
-Melissa