Is he new to your household? Kaji was like that at first too. There is a few things he acts like he doesn't understand. It really just takes time. We started with Monster too, he plays fetch now (inside and outside) and I sometimes put his toys inside a shoe box and he has to find it.
Just be creative with what you have.
PS Kaji doesn't know how to play tug. I got him a cat toy (mouse) and he's kinda learning. Too bad he lost it already.
