So I was trying to from Germany as Prussia. I got to a certain size and thought "huh, I should be able to form the Kingdom of Prussia at this point". I go onto the intrigue tab and see that the 'Found a New Kingdom' cannot be pressed. I have all of the conditions met except for the "High Chiefdom of Prussia is permitted to be the base for a custom kingdom" is this due to one of the ingame rules? is there any way of meeting this condition?