Why did I get API error code 10600?

PayPal returned API error code 10600 - Authorization voided.

The authorization you're trying to perform on a DoAuthorization, DoCapture, DoReauthorization, DoVoid or UpdateAuthorization has already been voided and can't be used because it's no longer valid.

Close the order or authorization.

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

See also:
DoAuthorization API Operation (NVP and SOAP)