18Rabbit

I have cleared and fully explored all of the Archmage's manor. I have recovered the missing drool covered crystal gem, I have learned the combination to the vault from the Tattered Note and viewed the soul in the lab but when I try and open the vault door it doesn't bring up the interact dialogue. When I mouse over the door, in red text it says "Unlocking this will require the proper key." and when I click on it, in the combat log it gives the same message in white text. Am I missing something?