I taught my Aussie, Mojo, to play with toys by using a clicker. He thought toys were beneath him until then. lol
You're going to think I'm crazy with what I did for my dogs that already enjoyed playing. lol I would pick a special "toy". That toy would be kept up out of reach and at first I would only pick it up randomly and act really excited about it. I do this on and off during the day, making sure the dog was paying attention, for about a week.
After the dog realised this was an exciting thing, I would start including the dog after picking it up and getting excited about the toy. I would always put the toy back afterwards, since it was a SPECIAL toy, not one of those meager everyday toys.
After lots of interaction like this, I would start using playtime with the toy as a reward for the dogs 'work'. The more hyped up you get about the toy, the more excited the dog will be.
It also helps if you have an idea of what kind of toy the dog prefers. Mojo loved tuggies, but Faust(GSD) and Zeo(BC/Sheltie) loved balls & frisbees. So learn what his preference is and then build on that. Being a GSD, I'm sure that he won't need too much encouragement to "turn on" to a certain toy anyways. lol Good luck with him!
