I have a theory on why Kitty Pryde (Kate Pryde) can not go through the gates to Krakoa. Her DNA has been altered by Dr Doom when he restored her after being attacked by the Marauders. He did that so that she could not affect his electronics and Doombots. Because of this change it probably would be logical that she would not be able to be resurrected by the Five. To resolve this the X-Men would probably have to find an old DNA sample probably at the mansion or from her mother before her attack from Harpoon.