Antidote quest unavailable?

[ratgills]

The game was working just fine for me until I talked to Faustus: after his dialogue, I am supposed to talk to him again to unlock the antidote quest, however he does not have any dialogue options available (other than 'goodbye'). I tried restarting my PS4 multiple times and even reloaded a save file from earlier in the game but I still cannot get the quest. Is there anything I can do without having to restart a new game file?