Developer prompt wont work?

Im trying to make it where when you buy the developer product you gain 5 walk speed but i cant find the problem here. please help if you can

local MarketplaceService = game:GetService("MarketplaceService")
local buyButton = game.StarterGui.ScreenGui.fiveWalkspeed
local productId = 63904167
local Ployer = LocalPlayer.Humanoid

buyButton.MouseButton1Click:connect(function()
    MarketplaceService:PromptProductPurchase(player, productId)
    walkspeed = walkspeed + 5
end)