Why can't I use _G for adding points to player's leaderstats?

So, I've been experimenting with _G and I think it's broken for a reason: when I first tried to print some object's name, it printed it; I don't know why but it doesn't print that anymore but instead prints 'nil'. I also can't understand why it doesn't work for adding points to a player's leaderstats. Here's my code in the first script:

game.Players.PlayerAdded:Connect(function(player)
    local LS = Instance.new("Folder", player)
    LS.Name = "leaderstats"

    local T = Instance.new("IntValue", LS)
    T.Name = "Test"

    _G.Test = T.Value
end)

Here's the second:

script.Parent.MouseClick:Connect(function()
    _G.Test = _G.Test + 25
end)

They both are in different locations: the first one is in the ServerScriptService, the second is in a part in the workspace. Please explain why won't it work.