Plutonium

Is Multiplayer a requirement? I had plutonium work previously on a machine without multiplayer or single player installed, just zombies. I recently tried to launch the game via plutonium and I encountered this error message when it previously worked. This install worked in June this year. I hadn't tried to use plutonium since then until recently.
It is frusturating that despite plutonium having a "lan" mode, you need to be online to log into plutonium. I suppose it doesn't matter now since I keep getting this error.