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! :)