If you're on the step where you want to place all the ultimate staffs in the robot head and the fire one in the main room, and you're on solo it won't spawn, or if you're on easy, it won't spawn. On two player it will. I think it's because one step requires one person to be near the cracked surface to call the airstrike in on while the other person needs to be in the head to push the button, so maybe it's locking you out to progress further?. So can you get the iron fist on easy?? Because me and my brother are playing local on easy and we can't get the staff in the robots head..