The Unknown status indicates that Fusebill was unable to fully process a response from the Payment Gateway. This results in a payment that must be manually resolved by a user. This will prevent further transactions from occurring until it has been resolved. When the Fusebill system does not receive a response, or there is an error that occurs during the handling of the payment, the unknown status is used instead of success or failure. This is to indicate that the system is unsure of how the payment ultimately resolved within the gateway.