INPUTS do not go in standard actors. They go in either Character Class, Controller Class, or for testing purposes the Level BP (not recommended).
Replication (RPC’s) will only call the server if the Actor calling the RPC is owned by the Player. Again Character, Actors attached to the character, Actors spawned by the character, OR the controller.
In character or controller, get a reference to Cards_Rep. Using that reference call On Se.