Am I doing this properly, if so is it cause the game is FilteringEnabled?

I was wondering if anyone can tell me why this doesn't change the Parent of the Vehicle to the Player's character, but yet it does the other stuff like giving the GUI to the Player, and if I'm doing it properly, is it cause the game is FilteringEnabled? Script is in a ServerScript in the VehicleSeat.

Script(I didn't make it, just edited it.):

script.Parent.ChildAdded:connect(function(w)
	if w:IsA("Weld") then
		if w.Name == "SeatWeld" then
			if w.Part1.Parent:FindFirstChild("Humanoid") then
				pl = game.Players:GetPlayerFromCharacter(w.Part1.Parent)
				if pl then
					if pl.PlayerGui:findFirstChild("SirenControl") then
						pl.PlayerGui:findFirstChild("SirenControl"):Destroy()
					else
						script.Parent.Parent = pl.Character
						local newgui = script.Parent.SirenControl:clone()
						newgui.Parent = pl.PlayerGui
						newgui.Frame.CarName.Value = script.Parent.Parent
					end
				end
			end
		end
	end
end)