Ellie’s Suburbs Joke

I’m so confused. I follow the hints but for the life of me Henry will not go up to the graffiti after the sewer, so I can’t trigger that conversation, which means Ellie won’t tell her joke. Iv restarted multiple times, and even made an entire new game and replayed all the way up to that point but nothing. I walk up to it and he says nothing or won’t go over there. It’s all I need for a platinum. Any help?