GUI, Prompt Purchase?

Output: 22:08:49.990 - MarketplaceService:PromptPurchase() second argument is not a valid productId (supplied productId was less than 0

local player = game.Players.LocalPlayer
local productId = script.Parent.Parent.Parent.Value.Value
script.Parent.MouseButton1Click:connect(function()
	game:GetService("MarketplaceService"):PromptProductPurchase(player, productId)
end)

You should only have one .Value in line 2 unless there's an object named Value