Filtering Enabled intro gui script won't work I don't know why?

The script is suppost to show a gui when you join a game but that's not the case for some reason. Everytime I test it, it won't work.

local script:

local Players = game:GetService("Players")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
 
local player = Players.LocalPlayer
local playerGui = player:WaitForChild("PlayerGui")
local welcomeScreen = playerGui:WaitForChild("WelcomeScreen")
local welcomeMessage = welcomeScreen:WaitForChild("WelcomeMessage")
 
local welcomeMessageEvent = ReplicatedStorage:WaitForChild("WelcomeMessageEvent")
 
local function onWelcomeMessageFired()
	welcomeMessage.Visible = true
	wait(5)
	welcomeMessage.Visible = false
end
 
welcomeMessageEvent.OnClientEvent:Connect(onWelcomeMessageFired)

Script:

local Players = game:GetService("Players")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
 
local Event = ReplicatedStorage:WaitForChild('WelcomeMessageEvent')
 
local function onPlayerAdded(player)
	Event:FireClient(player)
end
 
Players.PlayerAdded:Connect(onPlayerAdded)