I can't complete "Joining the Legion" for some reason, i go to Fort Hraggstad to clear it and after i've cleared it of everybody nothing happens and i can't proceed any further. Also i noiced that there was no quest marker for it either. Since i can't complete this quest it also causes me not to be able to talk to General Tullias for the "Season Unending" main quest because i can't talk to him about agreeing to go to the peace council. So basically i can't complete the Civil War questline or the main quest line. I may be able to join the sormcloaks and defeat the Imperials but i don't want to side with them.

This is pretty bad bug since it makes it impossible to complete the main questline or the civil war questline. And it all happened because i can't clear the fort for some reason.