Multiplayer doesn't work for literally half the day, for no apparent reason. Not from server overload, not 'cause of technical difficulties.
Pressing the home menu in single player works fine, but disconnects you in multiplayer while also putting you in "limited mode" (means ya can't play online). Even if ya reconnect and limited mode turns off, you're typically unable to play for a few hours if not a full day.
While on the topic'a slandering Ubisoft's latest release, Ubisoft forget t' turn on multiplayer in some areas of the Middle East (India in particular I recall) for a month or so. Ubisoft really ****ed up the multiplayer, pre- and post-release.