Why did I get API error code 10416?

The transaction failed and subsequent retries have expired the token. In the event of a failed transaction, don’t retry the DoExpressCheckoutPayment API call.

An Express Checkout token is valid for 10 transaction attempts or three hours, whichever occurs first.

To resolve this error, restart the Express Checkout process from the beginning with a new SetExpressCheckout request.

PayPal NVP and SOAP API Reference Guides.

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