Why dosen't this dev product script not work anymore?

I think it's because you didn't check whether a player has the dev product Note you can change some scripts to your preference

local MarketplaceService = game:GetService("MarketplaceService")
local DataStoreService = game:GetService("DataStoreService")
local Players = game:GetService("Players")
 
-- Data store for tracking purchases that were successfully processed
local purchaseHistoryStore = DataStoreService:GetDataStore("PurchaseHistory")
 
-- Table setup containing product IDs and functions for handling purchases
local productFunctions = {}
-- ProductId 123123 for a full heal
productFunctions[123123] = function(receipt, player)
	-- Logic/code for player buying a full heal (may vary)
	if player.Character and player.Character:FindFirstChild("Humanoid") then
		-- Heal the player to full health
		player.Character.Humanoid.Health = player.Character.Humanoid.MaxHealth
		-- Indicate a successful purchase
		return true
	end
end
-- ProductId 456456 for 100 gold
productFunctions[456456] = function(receipt, player)
	-- Logic/code for player buying 100 gold (may vary)
	local stats = player:FindFirstChild("leaderstats")
	local gold = stats and stats:FindFirstChild("Gold")
	if gold then
		gold.Value = gold.Value + 100
		-- Indicate a successful purchase
		return true
	end
end
 
-- The core 'ProcessReceipt' callback function
local function processReceipt(receiptInfo)
 
	-- Determine if the product was already granted by checking the data store  
	local playerProductKey = receiptInfo.PlayerId .. "_" .. receiptInfo.PurchaseId
	local purchased = false
	local success, errorMessage = pcall(function()
		purchased = purchaseHistoryStore:GetAsync(playerProductKey)
	end)
	-- If purchase was recorded, the product was already granted
	if success and purchased then
		return Enum.ProductPurchaseDecision.PurchaseGranted
	elseif not success then
		error("Data store error:" .. errorMessage)
	end
 
	-- Find the player who made the purchase in the server
	local player = Players:GetPlayerByUserId(receiptInfo.PlayerId)
	if not player then
		-- The player probably left the game
		-- If they come back, the callback will be called again
		return Enum.ProductPurchaseDecision.NotProcessedYet
	end
	
	-- Look up handler function from 'productFunctions' table above
	local handler = productFunctions[receiptInfo.ProductId]
 
	-- Call the handler function and catch any errors
	local success, result = pcall(handler, receiptInfo, player)
	if not success or not result then
		warn("Error occurred while processing a product purchase")
		print("\nProductId:", receiptInfo.ProductId)
		print("\nPlayer:", player)
		return Enum.ProductPurchaseDecision.NotProcessedYet
	end
 
	-- Record transaction in data store so it isn't granted again
	local success, errorMessage = pcall(function()
		purchaseHistoryStore:SetAsync(playerProductKey, true)
	end)
	if not success then
		error("Cannot save purchase data: " .. errorMessage)
	end
 
	-- IMPORTANT: Tell Roblox that the game successfully handled the purchase
	return Enum.ProductPurchaseDecision.PurchaseGranted
end
 
-- Set the callback; this can only be done once by one script on the server! 
MarketplaceService.ProcessReceipt = processReceipt