You’re using a sequence and casting / printing at the same time. Sequence nodes run the code in parallel, so you’re trying to assess the variable before its reference is actually cast.
Put the branch and print after the cast in the execution flow.
You’re also using “ref player” wrong. You have to have a valid reference to your robot somehow before you cast, so that input end (Object) is where you need to plug in your GetPlayerCharacter node.