Facebook connect issue

When a user initially uses facebook sign on for the the first time to join my site it works, but if they were to return again they get the following error:

 

Facebook Connect
Sorry but a profile with this email address already exists
 
Any ideas what could be causing the issue here?
Quote · 12 Dec 2013

it must connect to facebook and then again on your site and put facebook connect

Quote · 18 Dec 2013
 
 
Below is the legacy version of the Boonex site, maintained for Dolphin.Pro 7.x support.
The new Dolphin solution is powered by UNA Community Management System.