Error in MarketplaceService:PromptPurchase()?

I have following Script, which is placed under a ScreenGui in StarterGui. It is supposed to tell a player to buy a T-Shirt forever until they do, unless they are on the ExemptPlayers list.

local AccessShirt = 317838472 --ID of your group's access shirt 
local Player = game.Players.LocalPlayer
local ExemptPlayers = {'GShocked','TCAPI'} --Any players you choose to be exempt of payment
local PlayerExempt = false

for i = 1, #ExemptPlayers do
	if Player == ExemptPlayers[i] then
		PlayerExempt = true
		print("Exempt player joined!")
	end
end

repeat
	game:GetService('MarketplaceService'):PromptPurchase(Player, AccessShirt)
	print("Player hasn't bought")
	wait(1)
until PlayerExempt == true or game:GetService("MarketplaceService"):PlayerOwnsAsset(Player, AccessShirt) == true

This, however, returns the following error:

MarketplaceService:PromptPurchase() player should be of type Player, but is of type nil

Fixed Code:

local AccessShirt = 317838472 --ID of your group's access shirt 
local Player = game.Players.LocalPlayer
local ExemptPlayers = {'GShocked','TCAPI','MushyLesx'} --Any players you choose to be exempt of payment
local PlayerExempt = false
local Purchased = false

for i = 1, #ExemptPlayers do
    if Player.Name == ExemptPlayers[i] then
        PlayerExempt = true
        print("Exempt player joined!")
    end
end
 
script.Parent.MouseButton1Click:connect(function()
	game:GetService("MarketplaceService"):PromptProductPurchase(Player, AccessShirt)
end)

while Purchased == false do
	if PlayerExempt == true or game:GetService("MarketplaceService"):PlayerOwnsAsset(Player, AccessShirt) == true then
		script.Parent.Parent:Destroy() --Destroy the ScreenGui blocking you from entering
		Purchased = true
	else
		print("Player canceled purchase.")
	end
end