Amsbmm1945 this loop sometimes happens. What exactly causes it? Others have reported they could login with FB after a restart, other reported it took a couple days. A workaround is to logon with an email. If you do not have that then you can add an email here on the portal site.
-Login with FB on portal
-go to your profile page and
-find [connect accounts]
-add an email (use a real email and one you have not used before for a different diggy account)
-with that email you can now login to the mobile device