Look at the exception’s code point:
As you can see, the reason of the exception is the transaction decline on the PayPal side.
You can look for the exact error code and message in the exception.log
file.
A message has the following format:
exception ‘Magento\Framework\Exception\LocalizedException’ with message ‘
<error short name>
:<error code>
-<error description>
’ in vendor/magento/module-paypal/Model/Payflowlink.php:
For example:
exception ‘Magento\Framework\Exception\LocalizedException’ with message ‘CVV2 Mismatch: 15004-This transaction cannot be processed. Please enter a valid Credit Card Verification Number.’ in vendor/magento/module-paypal/Model/Payflowlink.php:388
You can look for an error code’s exmplanation in the official PayPal «API Error and Warning Codes» reference.
For example: