As far as I know, the cross server GNW NPC is bugged. You could just go to normal GNW NPC and check your group ranking in last week's war(based on points from wednesday if i am correct). If you are in top 16 in your server your group qualifies for GNW(which obviously you will )..I am not sure whether it needs additional registration, but think you dont need it because it's based on qualification from the top 16 in your previous GNW for which you have registered.

My group gnw npc is sayiing this. but I am unsure about this stuff, whether registering again for normal GNW would affect X-server GNW. It's confusing.