creating a kingdom

So I tried out a rock bottom bandit playthrough. Using my enemies' javelins and rocks, raiding paesants and caravans I slowly built up to the point that I now own a castle, but I'm still indipendent. The point was to grab a castle, found a kingdom, and get certain policies that allow me to build...

So I cant create a kingdom cause the game says I don't have a fief, nor am I independent. I DO in fact own a fief and am independent. I've looked online and tried the thing where I join a faction just to quit it and retain my fiefs, but it doesn't even offer me the 'retain fiefs' whilst quitting...

I’m brand new to this game, didn’t play the first one and other than the “Total War” series (which I really enjoy) I’ve never played a game like this. My question is this; I’m on the part where I’m trying to meet the requirements for creating my own kingdom. One of which is that I need to...