Why did I get API error code 13602?
PayPal returned API error code 13602 - Refund failed due to insufficient funds in your PayPal account.
PayPal can't refund the transaction because the PayPal account balance is less than the transaction amount.
Log in to your PayPal account to verify that you have adequate funds to cover the refund you're issuing. If not, add funds to the account.
Note: See the Developer Portal for a complete list of NVP/SOAP API error codes.