How to Allow Duplicate Developer Product Scripts?

I'm trying to use this same script for other Developer Products. If I use this script more than once, the Marketplace Service won't work. Any help on how to fix this?

local MarketplaceService = Game:GetService("MarketplaceService")
local ds = game:GetService("DataStoreService"):GetDataStore("PurchaseHistory")

MarketplaceService.ProcessReceipt = function(receiptInfo)
    print("Testing Receipt Loaded")
    local playerProductKey = "player_" .. receiptInfo.PlayerId .. "_product_" .. receiptInfo.ProductId --Should I change this manually with something?
    local numberBought = ds:IncrementAsync(playerProductKey, 1)
    for i,v in pairs (game.Players:GetChildren()) do
        if v.userId == receiptInfo.PlayerId then
            if receiptInfo.ProductId == 19918045 then
                print("Did this succeed?")


                lds = v:FindFirstChild("leaderstats")
                if lds ~= nil then
                    cs = lds:FindFirstChild("Coins") 
                    if cs ~= nil then
                        cs.Value = cs.Value + 100
                        print("Coins Sent") 
                    end
                end
            end
        end
    end
    return Enum.ProductPurchaseDecision.PurchaseGranted     
end