I have the same problem with Harry, cant get his third CG. I was positive and didnt tell him about the murder in the forest, and also said positive in the one dialogue outside the chalet. After that, I didnt get any other dialogue choices. When running into him in the shower or knocking on his door, the dialogue was just automatic. When I look at him at the BBQ, he looks away and I stay alone.
Obviously you are just a player (and thanks a lot for taking the time to reply) but im not sure what else to do