Facebook Plugin – login error when trying to log in

Hi Guys,

Trying to force the users of my site to use facebook to login (to stop password sharing)

I am getting an error:

Unable to load the registration form for ulti.TV. You may have previously blocked this app on Facebook. Go to your Facebook privacy settings to unblock this app. (Error: That ‘redirect_uri’ isn’t allowed for that client_id.)

at my URL

http://new.ulti.tv/wp-login.php?action=register

Any suggestions on how to fix this?