Some - though not all, it must be stressed - players have been experiencing a game-breaking bug in the Equilibrium quest, where a quest specific slime isn’t being spawned. The slime is supposed to drop a key ingredient required to complete the quest, and without the quest stays permanently uncompleted.
That has two knock one effects: one), the story cannot be progressed further, and two), the affected player is locked out of co-op play which is a big deal with the upcoming co-op events.
While a fix is undoubtedly in the works, it might be worth holding off on starting Equilibrium until then. We’ll keep you updated if and when the issue is fixed or a work around is discovered.