Button in ScreenGui is returning nil?

I'm messing around with RemoteEvents at the moment, trying to get a better understanding of how it works. But I don't exactly understand why button is returning nil?

Local Script

local button = script.Parent

button.MouseButton1Click:Connect(function()
	print(button)
	game:GetService("ReplicatedStorage").TestEvent:FireServer(button)
	
end)

Server

local repStorage = game:GetService("ReplicatedStorage")
local event = repStorage:WaitForChild("TestEvent")

event.OnServerEvent:Connect(function(player, button)
	print(player, button)
end)

The output is Player1 nil