If you are getting an Unauthorized error while processing order or payment via 2Checkout; chances are the cause of this problem could be that you incorrectly entered your API credentials to your website payment extension.

Check your 2Checkout payment extension to be sure the following are correct:

  1. Account Number
  2. Secret Word
  3. Private Key
  4. Publishable Key

This notice can also happen when the billing address is not filled out during checkout. The billing address is required, so hiding or removing it will cause the transaction to fail.