Thank you for the screenshots - they help a lot!
I see that you are setting the GameInstance (DuckDuckGame) → PlayerName variable from the MainMenu widget’s text entry box, and
I also see that you’re getting the name back from the GameInstance PlayerName where you stored it, and then updating the nameplate on all clients.
BUT…
You are getting the Client’s GameInstance and it’s only PlayerName variable, and you’re doing that on all the nameplates on that client.
The effect then is that every client will set all nameplates that exist on their machine, to whatever that client has stored in the one PlayerName variable on that client’s one GameInstance. Nobody will know what anyone else’s name is.
You’re having the server tell all the clients to set their nameplates, but you’re telling all the clients to set all their nameplate actors to the name that the client has set on their own GameInstance.