Switch Has Autority is just a “branch” to know or to choose what happen when something is called, if the code is called on the server then that will be the authority, if a client call it it will be executed on the client side, in this case the actor overlap so is the client to call that, this is why you receive always “Not Authority”. you need two custom event, one is Execute on Server, the second one is a multicast, you tell the server to destroy the actor, the server destroy it but in this case only the server know that the actor has been destroyed right? So now you can call the multicast event at the end of the Execute on Server event, with the multicast you tell other clients that the actor is actually destroyed.
try to go inside the overlap with the server as a player and you will notice that him have the authority.