Bless you for rescuing this little one! It sounds like he is in dire need of a loving home.
I have not been in your situation specifically, but I do know that some dogs simply don't like to play. If he was punished for puppy antics, it may take a long time, a year or more, before he is comfortable doing these things again.
Have you tried taking him to a park where he can explore a bit? I haven't met a dog who could resist chasing a ball thrown outside.
