Forum:Knoxx Vault won't open! Wtf?

Hey there, I was doing some regular armory farming, and just finished killing knoxx, I was kind of impatient so I Siren-d my way up the stairs and towards the door (The big one, not the code lock one), but the door wouldn't open. I have Super-Marcus-Sweep as my mission, so normally the door would be open, right? What's wrong here?