Same script works in one game but not in the other..?

There is no need for me to paste the contents of the script, because when I put it in another game it works perfectly fine, but when I put it in the game I want, it doesn't work. Well, I should probably put the script in anyways because it would be hard to know what I'm talking about without it. (ids replaced with (id))

local mps = game:GetService("MarketplaceService")
local chicken = (id)
local bucket = (id)

local datastore = game:GetService("DataStoreService")
local Previous = datastore:GetDataStore("Previous")
local storage = game:GetService("ServerStorage")

mps.ProcessReceipt = function(receipt)
	print("Bought")
	local id = receipt.PlayerId.."-"..receipt.PurchaseId
	
	local success
	pcall(function()
		success = Previous:GetAsync(id)
	end)
	
	if success then
		return Enum.ProductPurchaseDecision.PurchaseGranted
	end
	
	local player = game.Players:GetPlayerByUserId(receipt.PlayerId)
	
	if not player then
		return Enum.ProductPurchaseDecision.NotProcessedYet
	else
		if receipt.ProductId == chicken then
			print("Bought chicken")
			local chicken = storage:WaitForChild("Chicken"):Clone()
			chicken.Parent = player.Backpack
		end
		if receipt.ProductId == bucket then
			local bucket = storage:WaitForChild("KFC"):Clone()
			bucket.Parent = player.Backpack
		end
		pcall(function()
			Previous:SetAsync(id,true)
		end)
		return Enum.ProductPurchaseDecision.PurchaseGranted
	end
end

I get errors saying things like "purchase is already being processed" and "datastore queue is overflowed" and stuff, but here's the kicker. Whenever I put it in a different game, it works perfectly. If it helps, there is a donation board in the game that also uses the ProcessReceipt function, does this affect this script in any way?