Key name is too long?

Below, you'll find a portion of my script. When I went to test it in-game, it gave me the error 'key name too long'. Any tips? (Yes, this is for Dev products)

MarketplaceService.ProcessReceipt = function(receiptInfo) 

    -- find the player based on the PlayerId in receiptInfo
        if p.userId == receiptInfo.PlayerId then


            -- check which product was purchased
            if receiptInfo.ProductId == id then
                n = p.Name

        end
    end 

    -- record the transaction in a Data Store
    local playerProductKey = "player_" .. receiptInfo.PlayerId .. "_purchase_" .. receiptInfo.PurchaseId
    ds:IncrementAsync(playerProductKey, 1)  --error is here

    -- tell ROBLOX that we have successfully handled the transaction
    return Enum.ProductPurchaseDecision.PurchaseGranted     
end

    end
end)