Why did I get API error code 10602?
PayPal returned API error code 10602 - Authorization completed.
The authorization has already been completed. The following API calls can produce this error: DoAuthorization, DoCapture, DoReauthorization, and DoVoid.
Use the GetTransactionDetails API call to check the status of the transaction. If your authorization is pending, you can try to capture it.
For help resolving this issue or others, visit PayPal's Contact Customer Service page.
GetTransactionDetails API Operation (NVP)
GetTransactionDetails API Operation (SOAP)
API error codes