I can't pretend to know why or how this worked but I've tried the steps mentioned in this thread with success but replaced my phone and the fix no longer worked. I started trying anything and with a pin lock screen enabled and the WiFi version of the certificate installed I tried to encrypt the phone under security which forces you to change to an alpha/numeric password. If you do it with less than 80% it will not encrypt the phone. If you go back into settings it should let you set any lock screen option without having to delete the foxfi certificate. Maybe someone else can explain why this worked. Good luck.