When you have your NT ready, u click it and if it gives u the next message:
Nation Transfer failed. Please try again later.
Dont panic, just go to the 3 chars in the account and clean the Friend lists from the accounts. (OFC leave the clans also).
Im posting this because many people didnt know as well as i didnt.
Tako0606 - Warrior from manes, who told me about how to fix this.