Norcold 510 help

I have a Norcold 510 refrigerator in my truck camper. The temperature setting won't change from 8. I have the manual and followed the instructions. When you hold the temp setting button it is supposed to change from 1-9 and you let go at the setting you want. Mine stays on 8. Am I missing something or is this a common issue and easy fix? There are no error codes.