Quest interrupted - PvZs GW2 [ Edited ]

[Radarlover18]

There is a passage opening in Crazy Dave’s garage in one of the single player quests.  When I invited a friend to join the game, the passage in the garage wasn’t there anymore.  When I go back to single player, it’s still gone and I am unable to re-open the passage way in the garage.

Any suggestions on how to get back to that point without starting everything over again?