Why did I get API error code 10486?
PayPal returned API error code 10486 - This transaction couldn't be completed.
Cause
A buyer’s Express Checkout payment failed due to a bad funding source; for example, the transaction exceeded the buyer's card limit.
Solution
If you send your buyer to the PayPal page to select an alternate funding source or add a new funding source, this eliminates the need to perform another SetExpressCheckout call that reinitiates the entire transaction flow. It also helps the buyer to complete the transaction (instead of getting stuck in an endless checkout loop).
Note: The initial card failure occurred when the card-issuing bank denied the transaction. If the customer feels that the denial was in error, ask them to contact their bank to resolve the issue.
See the Developer Portal for a complete list of NVP/SOAP API error codes.