A lot of dogs have trouble with returning the ball, but normally dogs love to chase things... does he ever chase things? Do you have alluring toys that squeak?
A couple things: make sure he's super energetic when you want to play, and don't go get the toy, because then he might learn that the most efficient way to get his toy is to wait for
you to fetch it.
Maybe collect a dozen toys (rolled up socks are good too), and throw them, one by one. Also, are you throwing them far enough away, and away from him? I generally throw the toys down a hallway.