you need to make progress with all characters patriciped in attack, update police oficier site, talk with oficiers, find stronghold of assassins i don't know, if it is neccesary, but made progress with sandra (I usually end up all main group character storylines at first) then find strange gold in Amagal, and check other quests, then it must work, if not help check walkthrough, becouse I am not wikipedia and I don't know everything