I think the best advice is to be persistent and never stop trying! My pup wasn't a rescue, but he didn't seem to know what to do with toys. It took months for him to want to play with me (like chase), and a few more months for him to play with toys. A total of a year for him to play fetch correctly; and I have yet to figure out how to teach him tug. He just doesn't seem to understand the concept.
