god i had the same problem with barnaby's fail end CG...i failed more than 5 times to get it before giving up lmao, but i found a comment below me with the steps that helped me get it if you haven't seen it yet. hope this helps :)
(credit to @/Nokayo)
1st meeting (class):
"hi" & "comment on how interesting the play is"
2nd meeting (class):
"compliment barnaby's notes"
3rd meeting (6:00 PM library, work on class project with barnaby)
"disagree"
4th meeting: (6:00 PM library, work on class project with barnaby)
"go to the door"
he still avoids you if you try to approach him in class after this, but it should give you the CG you're looking for