Your function Toggle is not executed on clients because it isn’t called at all from a client – your Has Authority switch forbids it. Because a listen server would call this method, I assume that the server has the authority over the Usable Object, but not the client. Normally you would create (for example) a ServerOnUse function in your player controller or character and call it after you linetrace. This should be set to Run On Server and then calls the OnUse function. And when your lights are replicated, their status is updated on all client automatically.