Hello,
The Measurement and Automation Explorer (MAX) is the software interface for all National Instruments hardware products. This means that 3rd party hardware products (like your HPIB LAN device) will not be detected in MAX. Instead, you will need to use the driver software that you received from HP (or Agilent) to configure the device.
I hope this answer sheds some light on the situation. Good luck with your application, and have a pleasant day.
Sincerely,
Darren Nattinger
Applications Engineer
National Instruments