Why isn't this this script working?

So I'm confused because i did everything the roblox wiki told me to do in this script but it still doesn't work. Can anyone tell me why? Thanks if you did!

Script:

local plr = script.Parent.Parent.Parent.Parent
local MarketplaceService = game:GetService("MarketplaceService")
local cashid = 22957008
local PurchaseHistory = game:GetService("DataStoreService"):GetDataStore("PurchaseHistory")
 

function addcash()
	if plr then
		local leaderstats = plr:FindFirstChild("leaderstats")
		if leaderstats then
			local cash = leaderstats:FindFirstChild("Cash")
			if cash then
				cash.Value = cash.Value + 10000
			end
		end
	end
end

script.Parent.MouseButton1Click:connect(function()
	MarketplaceService.ProcessReceipt = function(receiptInfo) 
	    local playerProductKey = receiptInfo.PlayerId .. ":" .. receiptInfo.PurchaseId
	    if PurchaseHistory:GetAsync(playerProductKey) then
	        return Enum.ProductPurchaseDecision.PurchaseGranted --We already granted it.
	    end
	    -- find the player based on the PlayerId in receiptInfo
	    for i, player in ipairs(game.Players:GetPlayers()) do
	        if player.userId == receiptInfo.PlayerId then
	            -- check which product was purchased (required, otherwise you'll award the wrong items if you're using more than one developer product)
	            if receiptInfo.ProductId == cashid then
	                addcash()
	            end
	        end	
	    end
	    -- record the transaction in a Data Store
	    PurchaseHistory:SetAsync(playerProductKey, true)	
	    -- tell ROBLOX that we have successfully handled the transaction (required)
	    return Enum.ProductPurchaseDecision.PurchaseGranted		
	end
end)