The following conditions can produce error code 10423:

1. You set PaymentAction to "Sale" with SetExpressCheckout at the first API call.

• If you receive this error at the DoExpressCheckout API call, you can set PaymentAction to "Authorization." Because PayPal doesn’t allow this switch from “Sale” to “Authorization” in a single checkout session, use the same PaymentAction for the DoExpressCheckout API call that you used in the initial SetExpressCheckout API call.

2. Your API call failed because third-party permissions have not been set to make API calls on your behalf.

• Grant third-party permissions required to complete the API call. For many third parties, this is an automatic process when you connect your PayPal account to their administrative portal to receive payment.

3.  The email address on your PayPal business account is not confirmed or the account is not unverified.

• PaymentAction “Authorization” requires that your PayPal Business Account is verified with a confirmed email address. Reference “How do I confirm my email address” or “How do I verify my PayPal account” if necessary.

See the Developer Portal for a complete list of NVP/SOAP API error codes.