Have you finished ALL quests? The last one was the siege of Kock if I'm not mistaking. If you have done that (+ Spoken to the old landmeister), you should be landmeister already. Then it should indeed work to "parley" with other countries. The only country that says "Get lost" as far as I know, would be Mongolia (Spelled so?). Otherwise, I'm not really sure what might be wrong. Try restart the game?
