Why isn't my GUI popup script working correctly?

I'm trying to make a GUI that pops up when you click a part, but I don't want people to get tons of GUI's from clicking it over and over again. To fix this, I made a script which detects if the player already has the gui, but it isn't working. The script keeps coming back thinking that I still have the UI in my PlayerGui. This is the script:

local gui = script.Parent.MainframeGui

script.Parent.ClickDetector.MouseClick:Connect(function(Player)
		if  Player.PlayerGui:FindFirstChild("MainframeGui")  ==  nil then
		local gui = script.Parent.MainframeGui:Clone()
		gui.Parent = Player.PlayerGui
		gui.TimeRemaining.LocalScript.Disabled = false
	else
			print("Player already has the UI")
	end
end)

Any help would be appreciated! Thank you, have a great day and stay healthy! :)

You have to use the player argument which is already built into the event. Also, you had two gui variables, which were probably overwriting each other.

local gui = script.Parent:WaitForChild("MainframeGui")

script.Parent.ClickDetector.MouseClick:Connect(function(player)
	if player:WaitForChild("PlayerGui"):FindFirstChild("MainframeGui")  ==  nil then
		local guiClone = gui:Clone()
		guiClone.Parent = player:WaitForChild("PlayerGui")
		guiClone:WaitForChild("TimeRemaining"):WaitForChild("LocalScript").Disabled = false   
	else
		print("Player already has the UI")
	end
end)