Developer product script not working?

Hi guys! I made this script a few months ago and it was working fine....it is now not working :( Any ideas? Thanks!

local MarketplaceService = game:GetService("MarketplaceService")
local productId = 19750967
MarketplaceService.ProcessReceipt = function(receiptInfo) 

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

            if receiptInfo.ProductId == productId then

            player.PlayerGui.ChoosingMap.Frame.Visible = true
                       game.Workspace.ChooseMap.Value = true


            end
        end
    end 

    return Enum.ProductPurchaseDecision.PurchaseGranted     
end