Service Bus 2.6.6 Paired Namespace Enable Syphon

How to make work Paired Namespace receiver side to move messages from backlog queue to the primary queue. It seems to work with senders but with the receivers setting EnableSyphon = true does not seems to work. I can see always messages in the backlog queue and growing. All information that I could found is this Code Block , but since Service Bus 2.4Messaging.Factory does not have a Open Method.

factory = MessagingFactory.Create(SB_Primary_NS_Address);
factory.PairNamespace(new SendAvailabilityPairedNamespaceOptions
    {
        EnableSyphon = true,
        TransferQueueCount = 10,
        MessagingFactory = paired-NS_factory,
        NamespaceManager = paired-NS_manager
    });
factory.Open();