Make sure that you have only one Amazon account. Often a hubber will check a previous Amazon account used to place an order instead of checking the account that is affiliated with Hubpages.
If you do not have two Amazon accounts, do not despair. Periodically, Amazon sends out an email of earnings even if no revenue has been earned.
Also as I advise most of the information seekers on hubpages, do not hesitate to use the Hubpage search box and determine if other hubpage writers are having a problem checking Amazon revenues.