Unclassified error from the payment gateway: The gateway returned an unspecified error without a detailed explanation.
Unexpected system behavior: An unhandled exception or unknown failure occurred during transaction processing.
Temporary issues with third-party integrations: External systems involved in payment processing might be experiencing downtime or instability.
Advise the customer to retry the transaction after some time, as the issue may be temporary.
Recommend using an alternative payment method to complete the transaction.
Review transaction logs and API responses to check for any hidden error patterns or failures.
Contact the payment gateway support team for clarification and assistance in identifying the root cause of the unknown error.