I have a bluetick coonhound that I had to teach to play fetch. She wasn't a fetch dog she would chase the toy sometimes, but get there and ignore it or just not bring it back. Fetch is a great way to burn off energy and I really wanted her to play.
I used the clicker method when she would pick up the toy and come near by me I would click and she would get a treat. Eventually she realized that if she got it AND brought it back she would get a treat and now she really likes to play fetch.
Maybe clicker training would work for your dog learning to play too. Here is a link to a site that gives you info about clicker training.