Coins dev product wont work?

I have Two scripts that are suppose to make it so when you click a button it will ask if you want to buy something(with robux), and and when you click to buy it it will add to a leader stat(for the person who bought it).

this script is in ServerScriptService:

local MarketplaceService = game:GetService('MarketplaceService')
local devProductid = 391839362
MarketplaceService.ProcessReceipt = function(receiptInfo)
    for i, player in pairs(game.Players:GetChildren()) do
        if player.userId == receiptInfo.PlayerId then
            player.leaderstats.Coins.Value = player.leaderstats.Coins.Value +100 
        end
    end
    return Enum.ProductPurchaseDecision.PurchaseGranted
end

This is in the text button:

local devproductid = 391839362
local button = script.Parent
button.MouseButton1Click:Connect(function()
    game:GetService('MarketplaceService'):PromptProductPurchase(game.Players.LocalPlayer, devproductid)
end)