I've seen all of his summer league games except the first one. Part of the problem is he's just missing shots. The defense being played in this Summer League pales in comparison to some of the better defenses he saw in his senior year at UConn - they're giving him a ton of space on pick and rolls, and he just isn't making them pay. His shot looks a little bit flat - one of the announcers commented about a thumb injury, which I hadn't heard about.
Shot selection has also been a problem. He's taking a lot of shots early in the clock, that, while decent looks, aren't going to buy him a lot of good will with his teammates. Clearly, he's not going to have the same sort of leeway in the NBA that he did in college, so that's probably going to be an adjustment process for him.
I'm not too concerned about his jump shot, however, he appears to be forcing the issue in other facets of the game. He's over-dribbling, taking the ball too deep and getting swallowed up, and just generally trying to do too much.