Why won't this Developer Product script work?

So, I have this loading screen. It will eventually wait 1 min and then move on, for now you must pay 1 tix while I am developing the game. When I click the button, nothing happens. It should be doing all the devproduct stuff, and then making the current frame invisible, and the new one visible. Could someone tell me why it doesn't work? Thanks!

local MarketplaceService = game:GetService("MarketplaceService")
local productId = 22106513
loading = game.Players.LocalPlayer.PlayerGui.ScreenGui.loading
results = game.Players.LocalPlayer.PlayerGui.ScreenGui.results

game.Players.PlayerAdded:connect(function()
    print("start")
local DeveloperProducts = game:GetService("MarketplaceService"):GetDeveloperProductsAsync():GetCurrentPage()
for _, DevProductContainer in pairs(DeveloperProducts) do
    for Field, Value in pairs(DevProductContainer) do
        print(Field .. ": " .. Value)
    end
    print(" ")
end
print("end")
end)

MarketplaceService.ProcessReceipt = function(receiptInfo) 

    for i, player in ipairs(game.Players:GetChildren()) do
        if player.userId == receiptInfo.PlayerId then


            if receiptInfo.ProductId == productId then

                loading.Visible = false
                results.Visible = true

        end
    end 


    return Enum.ProductPurchaseDecision.PurchaseGranted     
end
end