Yes, the Display module plugs into an AquaBus port and gives you direct access to all settings even without a network connection.
Neptune just released AOS 5.06_7D21 yesterday to correct the bugs found in version 5.06_6E21 that was released 4 days ago. You should definitely update to this newest version, though the update will require a network connection, so getting your Apex back on the network will be critical.
Is your Apex using WiFi, or a network cable?
Also, have you tried rebooting your Internet router? This can sometimes resolve the issue of an Apex not communicating with Fusion.