You can't enter the wolves den if it's about the full moon event. Complete the full moon so you can proceed to "troubles in the den". Complete the step by step so you can have access to the cave.
I completed the full moon event, have Caleb in the farm along with finding the sample of the wolves in the misty abyss, it doesn't mention anywhere how to go into the wolves den however, specifically the second part where the beta wolf is
