Multiplayer Authentication Fix includes a registry fix that will update the IP address of the Nexus authentication server.
Nexus MP Patch
From the 15th of June, the Authentication server of Nexus is hosted on a
different IP. For the online multiplayer portion of the game to function
properly with all release versions, this registry patch must be executed.
Just unpack and execute it by double clicking it.
This patch has no effect whatsoever on the single player portion of the game
and is only needed when playing Nexus: The Jupiter Incident online.