Why is the server message not appearing?

I have a LocalScript inside a TextButton:

ocal playerGui = game.Players.LocalPlayer:WaitForChild("PlayerGui")
	 
function leftClick()
	local n = playerGui.OrderGui.Naem.TBO.Text
	game.ReplicatedStorage.VanillaMilkshake:FireServer()
	 print("VanillaClick")
	 playerGui.OrderGui.CurrentOrder.Text = "Vanilla Milkshake by "..n
	
end 


script.Parent.MouseButton1Click:Connect(leftClick)

And a Script inside ServerScriptService:

local playerGui = game.Players.LocalPlayer:WaitForChild("PlayerGui")
local n = playerGui.OrderGui.Naem.TBO.Text

game.ReplicatedStorage.VanillaMilkshake.OnServerEvent:Connect(function()
	
		
	game.StarterGui:SetCore("ChatMakeSystemMessage",{
		Text = "A Vanilla Milkshake has been ordered by "..n

})

end)

Why does no server message appear in chat?