He can't get through the wall that she puts up. And you know what? That's fine. It is what it is.
He did his best, and he made her happy at a time when she needed it. He should tell her how he feels, and be done with it. At some point, she needs to at least recognize how he feels. He's not just a client to her and she knows it, it will be on her to decide of she wants to be more than friends or not.