Chateau d'Onterre Arcane Horror Bug?

I had finally figure out how to get to the top of the balcony when I had to stop my game and go somewhere for a bit. Today when I logged into my character, the Arcane Horror wasn't spawned anymore and I can't get him to spawn?  I tried leaving the the whole dungeon and coming back but it still isn't there?  And the questline doesn't respawn so I'm not able to go through and get the clues and do the thing over again.  What should I do?! (I"m on Xbox One)