Lorraine I'm having the same problem here with little Abigail. She doesn't want to eat much but when I take baby food and mix the kitten chow in it she eats pretty well. I've also been giving her some chicken. She loves that! At this point I'm doing what I can to get keep her eating and this is working very well.
Are you feeding Popeye the same food that the vet gave him? If not he may not like the type you have. I have noticed that the kitties that have been on thier own are pretty picky since they are used to "fresh meat"
I would keep trying different things until you find what appeals to him the most and stick with that. I know we all try to give them the best foods but just like people food that stuff doesn't taste good sometimes!