I am putting a robux purchased item in my game but it won't work?

The robux purchased item I put into my game when clicked on says, "This is not for sale" How do I fix this. Is it script, or something else. Thank you in Advance.

Anyways, here's the script I put into server script service as "RobuxPurchaseScript"

local mpService = game:GetService("MarketplaceService")
local moneystatus50 = game:FindFirstChild("<|>ObbyBucks")

mpService.ProcessReceipt = function(purchaseInfo)
	local plr = game:GetService("Players"):GetPlayerByUserId(purchaseInfo.PlayerId)
	if purchaseInfo.ProductId == 465793789 then
		if moneystatus50 then
			moneystatus50.Value = moneystatus50.Value + 50
		end
		return Enum.ProductPurchaseDecision.PurchaseGranted
	end
end

Next is the script I put into the button

local button = script.Parent
local mpService = game:getService("MarketplaceService")

button.MouseButton1Click:connect(function()
	mpService:PromptProductPurchase(game.Players.LocalPlayer, 465793789) 
end)