Why isn't sonny (demi lavato) in the new so random show?

i was watching the new so random show on family channel and sonny isn't in it, but chad (sterling night) is. does anybody know why this is? because in the show "sonny with a chance"( which is where they got the idea for "so random") chad is in mackenzie falls and sonny is in so random. so i was wondering if anybody could explain to me why this is? anything is appreciated. please and thank you! :)