You killed Goroth too early.
When you first enter the zone, an NPC (I don’t recall which off hand) will be standing in front of the door to the Inquisition. After the initial event is triggered leading to Goroth spawning, this NPC will walk into the Demonic Inquisition room and close the door behind them. If that door has not finished closing before Goroth dies you will break the event script and the door will remain closed until the next raid reset.
Note you can engage Goroth before the door has finished closing and not cause any problems - you just can’t kill him before that.