Multiplayer Quest Progression Locked

I've been playing for a little while with a couple of friends and just went along with them not doing quests. Realizing that I needed to actually progress the questline at some point I went back to redo all of it, but when I get to kill the Jabberwock, there isn't one to kill anymore. We already killed it and now I can't even do that solo. Being in the party I was under the impression that we had our quests tied, but I never actually looked. I was just having fun. That is until this blunder.