I, and probably many others, would love to try to help, but you've given so little information. You probably couldn't have given us less relevant information if you tried
* Why did he leave his owner?
* How did you become his new owner?
* Is he healthy? Has he had a recent vet checkup?
* Where is he staying right now? Please describe his current accommodations. Do you live alone with him? Are there other humans or pets in the home?
* When you say he hasn't eaten, tell us about that. What have you attempted, and how has he responded? Not just the food itself, but how and where have you tried to feed him?
* When you say that he won't play, tell us about that, what have you attempted?
You obviously need to get him eating first. Everything else is secondary right now. If him not trusting you is the problem, then don't let that be a barrier right now to him eating. Make it nice and easy for him. Quiet room, no people or other pets in it, and preferably one or two types of foods that he has known to eat before. You can also try "jackpot" foods, like tuna from a can, or turkey or chicken from the deli.