Can't read him.

Maybe he has the ability to do that. My older sister has almost always had the power to see auras and she told me that one time when I was upset and crying, she wanted to know what was wrong but I didn't want to tell her. She said that once I noticed that she was in the room with me I kind of blocked my aura from her without even realizing it, and I still do it. Maybe he has an emotion that he doesn't want you or anyone else to see and is either hiding intentionally or unintentionally.