Stuck Character

Questing with friends, we just finish the Cemetery, but I cant go to Hunting grounds, or even enter the Cemetery "boss fight" area anymore. I'm on the quest to go to hunting grounds and the NPC into the cemetarry that trnasform into the boss is not there anymore (can't redo the boss fight). The gate to the boss area are open, and i still have my keys in my inventory. What do I do ?