Why does my code to send a message on chat by clicking on a gui not work?

No problems shows in the editor, i can't seem to be able to fix this.

local function leftClick()
	game:GetService("StarterGui"):SetCore("ChatMakeSystemMessage",{
	Text = ("Angry Munci has Spawned!");
	Color = Color3.new(255,255,255);
	Font = Enum.Font.Creepster; 
	FontSize = Enum.FontSize.Size18;
	})
end
script.Parent.MouseButton1Click:Connect(leftClick)