Why does "Admin" only get put into ServerScriptService in Studio, but not real game?

This is a Script in game.Workspace:

game.Players.PlayerAdded:connect(function(Player)

local SSS = game:GetService("ServerScriptService")
game:WaitForChild("ServerScriptService")

Player:WaitForChild("PlayerGui")

local PlayerGui = Player.PlayerGui

local AM = script.Admin
AM.Parent = game.ServerScriptService
AM.Disabled = false

local c = script.Login:Clone()
c.Parent = PlayerGui

end)

And this is a LocalScript that gets cloned to game.Players.PLR.PlayerGui.Login.PassBox:

script.Parent:TweenPosition(UDim2.new(0.5, -227, 0.5, -60))

script.Parent.Exit.MouseButton1Click:connect(function()
    script.Parent:TweenPosition(UDim2.new(0.5, -227, 2, 0))
    wait(1)
    script.Parent.Parent:Destroy()
end)

script.Parent.Login.MouseButton1Click:connect(function()
    local LoginVal = game.ServerScriptService.Admin.Login
    LoginVal.Value = script.Parent.PasswordBox.Text
    script.Parent:TweenPosition(UDim2.new(0.5, -227, 2, 0))
    wait(1)
    script.Parent.Parent:Destroy()
end)

So what happens is, the "Admin" script is supposed to get put into ServerScriptService by changing the .Parent property. It works fine in the Studio, but not in the real game. If anyone knows what's going on or how to fix it, please let me know. Please use code to answer it.