If it won't eat meals, it could mean it's not hungry, or it could be ill, or it could have a toothache.
If it won't play games, it might be at its minimum weight (they lose weight when they play games, and so won't play games if they're not heavy enough,) or it could be ill, or it could have a toothache. If he isn't ill or doesn't have a tooth ache, feeding him a snack or two will make him heavy enough to play games.
When they're ill, you'll see a skull in the upper right corner of the screen.
When they have a toothache, you'll see a tooth in the upper right corner of the screen.
When they're ill or have a toothache, give them medicine to make them better. Sometimes you have to give medicine several times to make them better.