How to buy money In-game with Dev Products?

I've Tried things and i changes a lot but its still not working, i just buy the products but don't get the money.

If i buy in-game 100 FrostyCoins/cash i will pay but i don't get the 100 Frostycoins/cash

What does i wrong?

The first 2 Scripts are from Roblox Wiki (I change somthings)

I tried all ready things.. But it not working and am search all some months for this. (Yes, My english is bad)

The Local Script is:

local buyButton = game.Workspace.Part1.SurfaceGui.a
local productId = 21118799
 
-- when player clicks on buy brick prompt him/her to buy a product
buyButton.MouseButton1Click:connect(function()
	game:GetService("MarketplaceService"):PromptProductPurchase(game.Players.LocalPlayer, productId)
end)

The script in workspace is:

local MarketplaceService = Game:GetService("MarketplaceService")
local ds = game:GetService("DataStoreService"):GetDataStore("PurchaseHistory")
local productId = 21118799
 
-- define function that will be called when purchase finished
MarketplaceService.ProcessReceipt = function(receiptInfo) 
 
	-- find the player based on the PlayerId in receiptInfo
	for i, player in ipairs(game.Players:GetChildren()) do
		if player.userId == receiptInfo.PlayerId then
 
 
			-- check which product was purchased
			if receiptInfo.ProductId == productId then
 
				-- handle purchase
				player.leaderstats.FrostyCoins.Value = player.leaderstats.FrostyCoins.Value + 100
			end
		end
	end	
 
	-- record the transaction in a Data Store
	local playerProductKey = "player_" .. receiptInfo.PlayerId .. "_purchase_" .. receiptInfo.PurchaseId
	ds:IncrementAsync(playerProductKey, 1)	
 
	-- tell ROBLOX that we have successfully handled the transaction
	return Enum.ProductPurchaseDecision.PurchaseGranted		
end

The Leaderboard script is:

print("LinkedLeaderboard script version 5.00 loaded")

stands = {}
CTF_mode = false -- I think there is something wrong with the capture the flag mode, VERY UGLY HACK is down near where it is leave false unless you can fix it.


function onHumanoidDied(humanoid, player)
	local stats = player:findFirstChild("leaderstats")
	if stats ~= nil then
		local deaths = stats:findFirstChild("WO's")
		deaths.Value = deaths.Value + 1

		-- do short dance to try and find the killer

		local killer = getKillerOfHumanoidIfStillInGame(humanoid)

		handleKillCount(humanoid, player)
	end
end

function onPlayerRespawn(property, player)
	-- need to connect to new humanoid
	
	if property == "Character" and player.Character ~= nil then
		local humanoid = player.Character.Humanoid
			local p = player
			local h = humanoid
			humanoid.Died:connect(function() onHumanoidDied(h, p) end )
	end
end

function getKillerOfHumanoidIfStillInGame(humanoid)
	-- returns the player object that killed this humanoid
	-- returns nil if the killer is no longer in the game

	-- check for kill tag on humanoid - may be more than one - todo: deal with this
	local tag = humanoid:findFirstChild("creator")

	-- find player with name on tag
	if tag ~= nil then
		
		local killer = tag.Value
		if killer.Parent ~= nil then -- killer still in game
			return killer
		end
	end

	return nil
end

function handleKillCount(humanoid, player)
	local killer = getKillerOfHumanoidIfStillInGame(humanoid)
	if killer ~= nil then
		local stats = killer:findFirstChild("leaderstats")
		if stats ~= nil then
			local kills = stats:findFirstChild("KOs")
			local cash = stats:findFirstChild("FrostyCoins")
			if killer ~= player then
				kills.Value = kills.Value + 1
				cash.Value = cash.Value + 1 -- change amount of money per kill here
				
			else
				kills.Value = kills.Value - 1
				
			end
		end
	end
end


-----------------------------------------------



function findAllFlagStands(root)
	local c = root:children()
	for i=1,#c do
		if (c[i].className == "Model" or c[i].className == "Part") then
			findAllFlagStands(c[i])
		end
		if (c[i].className == "FlagStand") then
			table.insert(stands, c[i])
		end
	end
end

function hookUpListeners()
	for i=1,#stands do
		stands[i].FlagCaptured:connect(onCaptureScored)
	end
end

function onPlayerEntered(newPlayer)

	if CTF_mode == true then

		local stats = Instance.new("IntValue")
		stats.Name = "leaderstats"

		local captures = Instance.new("IntValue")
		captures.Name = "Captures"
		captures.Value = 0


		captures.Parent = stats

		-- VERY UGLY HACK
		-- Will this leak threads?
		-- Is the problem even what I think it is (player arrived before character)?
		while true do
			if newPlayer.Character ~= nil then break end
			wait(5)
		end

		stats.Parent = newPlayer

	else

		local stats = Instance.new("IntValue")
		stats.Name = "leaderstats"

		local kills = Instance.new("IntValue")
		kills.Name = "KOs"
		kills.Value = 0

		local cash = Instance.new("IntValue")
		cash.Name = "FrostyCoins"
		cash.Value = 0 -- starting cash here =D

		local deaths = Instance.new("IntValue")
		deaths.Name = "WO's"
		deaths.Value = 0

		kills.Parent = stats
		deaths.Parent = stats
		cash.Parent = stats

		-- VERY UGLY HACK
		-- Will this leak threads?
		-- Is the problem even what I think it is (player arrived before character)?
		while true do
			if newPlayer.Character ~= nil then break end
			wait(5)
		end

		local humanoid = newPlayer.Character.Humanoid

		humanoid.Died:connect(function() onHumanoidDied(humanoid, newPlayer) end )

		-- start to listen for new humanoid
		newPlayer.Changed:connect(function(property) onPlayerRespawn(property, newPlayer) end )


		stats.Parent = newPlayer

	end

end


function onCaptureScored(player)

		local ls = player:findFirstChild("leaderstats")
		if ls == nil then return end
		local caps = ls:findFirstChild("Captures")
		if caps == nil then return end
		caps.Value = caps.Value + 1

end


findAllFlagStands(game.Workspace)
hookUpListeners()
if (#stands > 0) then CTF_mode = true end
game.Players.ChildAdded:connect(onPlayerEntered)