Yesterday afternoon, I migrated the site to a newer, faster server. Unfortunately, something I did broke the account link feature of the site and users who added their account were unable to perform the initial synchronization. The error these users were seeing was "We were unable to establish a successful session to your FFRK account".
I'm happy to say that this issue has been fixed and accounts can now be linked again. I had to delete the 9 "broken" linked account from the database so if you had the issue yesterday, please attempt to link your account again. It should work correctly this time. A huge thanks to the two players who reported the issue in the #ffrkcentraldotcom channel in the FFRK Slack chat.
I sincerely apologize for the inconvenience. Have a great day! :)