So it worked fine for me - when I click the login button, it asked me if I wanted to connect it to my facebook account, went through the checklist and everything works.
My business partner, who has the same WordPress admin privs as I do, clicks the Login button, same process of accepting access, same email address as facebook on his wordpress user account, but when he tries to go to the backend, he gets an error that he doesn't have Dashboard privs. He's disconnected and reconnected twice and it does the same thing.
He's also gone into facebook and deleted the app from his account and readded it through trying to log in. Same error.
I can go into the dashboard and it shows his facebook email address and User ID on his WordPress user account and his access level in WordPress is still shown as Administrator.