my mac doesn't automatically recognize my wi-fi

My mac automatically recognizes the wi-fi at my parent's house, but at mine, it says "none of your preferred networks are available." So I have to find mine in the list, click it, and then connect. What's the deal? It also doesn't seem to like the wi-fi at my work either for some reason. It appears like it is connected, but I can't access the web or Itunes match/cloud stuff..what gives?