Games : Can't get Ulfic Stormcloak to agree with the peace truce in "SEASON UNENDING"

Every time I try to talk to Ulfric Stormcloak he always tells me to talk to Galmar because he needs me to run an errand. But... Every time I try and talk to Galmar he always tells me something about Ulfric joining the Empire. They always redirect me to each other! I also can't start the "JAGGED CROWN" quest because this quest is getting in my way! It puts me in a constant loop of nothing! Any help would be appreciated! Thanks.