I just purchased the Primo water cooler model # 601130, and I can't locate the serial#. I only see a silver sticker in the back with the 1409020023. It is under the label that has the model# and product details. I am trying to register my dispenser online and it is not accepting it. I am wondering if there is a certain amount of #s/letters and/or particular letter/number sequence in the serial # to look for that is commonly among this model. Thank you