On a similar note, there are times when I will have Sims over, and only certain ones will be available for chess, or to play cards with. Sometimes, I will have just one over, and he's not available for chess or card games. Perhaps, there's a similar cause. Perhaps, they have unseen needs or moods, that are preventing them from responding to food or to play? Maybe, the Sim is full, and therefore won't eat, when called to a meal. Just a thought.