Why does a customer's payment have a status of Unknown?

The Unknown status indicates that Fusebill was unable to fully process a response from the payment Gateway. This results in a payment which must be manually resolved by a user, and will prevent further transactions from occurring until it has been resolved. When we do 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. It is to indicate that the system is unsure of how the payment ultimately resolved within the gateway. 

From within Fusebill, you will need to manually resolve the payment as either successful or failed. If you go to the payments tab on the customer, you will see a payment with a status of 'Unknown'. If you click into the details of that unknown payment, you will have the option of manually marking it as successful or failed. If you log into your gateway and find this payment, you will be able to see if it was successful or failed. If you are not able to find the payment at all, that likely means the gateway never received it and you should mark it as failed.