The Covenant mission Crusade: The Ennead is poorly designed.
The mission requires you to physically visit the entrance to the Ennead before you can progress the quest.
What happened to me was that I accepted the mission, joined a lobby to the Ennead, and entered the expedition through the Group Finder tool.
I completed the expedition successfully, and when I came back out, the mission had not progressed at all.
I went to the entrance to trigger the quest objective, but I THEN needed to do the Ennead again for the quest.
TLDR: Visiting the entrance to the expedition should be optional, and it should NOT block the progress of the mission.