So basically, a few months ago I made a dev product for 20 robux in my game that gives you coins. A lot of people bought it and even sometimes more than once. But now today I was working on more products using the same exact script, and when I bought it I didn’t get anything at all. So I have no idea if this has been going on the entire time. I copied a script from Roblox Itsself and put it in serverscriptservice, In output it keeps saying ’ Failed to process receipt: 
{…} attempt to call a nil value’
This is my script:
local MarketplaceService = game:GetService("MarketplaceService")
local Players = game:GetService("Players")
local productFunctions = {}
productFunctions[1574028110] = function(receipt, player)
local stats = player:FindFirstChild("leaderstats")
local gold = stats and stats:FindFirstChild("Coins")
if gold then
gold.Value = gold.Value + 200
return true
end
end
local function processReceipt(receiptInfo)
local userId = receiptInfo.PlayerId
local productId = receiptInfo.ProductId
local player = Players:GetPlayerByUserId(userId)
if player then
-- Get the handler function associated with the product ID and attempt to run it
local handler = productFunctions[productId]
local success, result = pcall(handler, receiptInfo, player)
if success then
-- The player has received their benefits!
-- return PurchaseGranted to confirm the transaction.
return Enum.ProductPurchaseDecision.PurchaseGranted
else
warn("Failed to process receipt:", receiptInfo, result)
end
end
-- the player's benefits couldn't be awarded.
-- return NotProcessedYet to try again next time the player joins.
return Enum.ProductPurchaseDecision.NotProcessedYet
end
-- Set the callback; this can only be done once by one script on the server!
MarketplaceService.ProcessReceipt = processReceipt
``