Draining messages from a Remote machine is not working

I have a MSMQ transactional topic and its respective subscriber party. From another machine (other than the one running Neuron) I can connect a Test Client to the publisher party and another one to the subscriber party. I can send messages that land on the subscriber queue (subscriber_topic queue) and are piled up there (not on Retry subqueue but in the main queue).

So, The publishing client in remote machine is successfully connected and is able to send messages; the client subscriber from the same remote machine is not draining any messages but is connected. 

If I start a Test client on the Neuron machine and connect it to the subscriber party, it drains all the piled up messages immediately.

I can't find anything in Neuron logs neither in audit logs for those parties, nor receive an error on the remote subscriber client.

I'm wondering why this Subscriber client on other machine than the one running Neuron is not receiving nor notified of new messages in the subscriber party that is connected to. Some ideas?