i made a notification system when a player joins,can someone fix this for me?

i have been working on this for like 3 hours and i still didnt fix the problem.. it doesnt runs it when a new player joins.

function onJoined(newPlayer)
game.StarterGui:SetCore("ChatMakeSystemMessage", {
        Text = newPlayer.Name.. " has joined the game!";
        Color = Color3.new(1, 1, 1);
        Font = Enum.Font.SourceSansBold;
        FontSize = Enum.FontSize.Size24;
})
script.Parent.join1:Play()
end

game.Players.PlayerAdded:connect(onJoined)