That's the normal registration flow when you have the "User Creation" setting set to "Full Joomla User". In this case, they will need to create a new account, or associate their Facebook user with an existing account on the site. Once done, the user will be able to login with either their Facebook account or their Joomla account.
If you don't want to make them fill out the form, and just want an automatic username created for them, change the User Creation setting to "Facebook User Only".
JFBConnect login-redirect error
