prompting product purchase on surface gui not working?

local mps = game:GetService("MarketplaceService")
game.Players.PlayerAdded:Connect(function(player)
	game.Workspace.SellCoins1000.SurfaceGui.Buy1000.MouseButton1Click:Connect(function()
			local productId = 1086368295
		game:GetService("MarketplaceService"):PromptProductPurchase(player, productId)
		mps.ProcessReceipt = function(receiptInfo)
			if receiptInfo == productId then
				player(receiptInfo.playerId)
				player.leaderstats.Coins.Value = player.leaderstats.Coins.Value + 1000
				return Enum.ProductPurchaseDecision.PurchaseGranted
			end
		end
		end)
		
	end)

Hello!

I am assuming the issue here lies simply in the Functions you are using via the MarketplaceService.

I did some organizing & redoing of your code!

I'm assuming that you are prompting purchase of a Developer Product or a Game Pass (within the game), so here is the code that should work for that.

-- Variables:
local marketplaceService = game:GetService('MarketplaceService')
local productId = 1086368295

local part = workspace:WaitForChild('SellCoins1000')
local button = part:WaitForChild('Buy1000')

local statsGain = 1000

-- onClicked Function:
local function promptPurchase(player)
	if not marketplaceService:UserOwnsGamePassAsync(player.UserId, productId) then --Making sure the player doesn't already own the game pass
		marketplaceService:PromptGamePassPurchase(player, productId)
		marketplaceService.PromptGamePassPurchaseFinished:Connect(function(player, purchasedId, bought)
			if purchasedId == productId and bought == true then
				print(player .. 'has successfully purchased something!')
				player.leaderstats.Coins.Value = player.leaderstats.Coins.Value + statsGain
			end
		end)
	end
end