Actors disappears when using parent function. What's wrong?

Another newb question from me
For some reason, some of the actors disappears from the screen when I use the "parent" function for a background with my player. Am I doing it wrong in some way, or can't you use the "parent" function like this?

For some reason, some of the actors disappears from the screen when I use the "parent" function for a background with my player. Am I doing it wrong in some way, or can't you use the "parent" function like this?