I've gotten this error code the vast majority of times when attempting to connect online. Several dozen attempts, with only 2 of them resulting in successful games, and one of them ending in an error code in the pre-game lobby. At first I thought it had something do do with last night's maintenance, but that's obviously not the case now.
I live on campus, so there's nothing I can do about the routers - but this problem has never occured with any other 3DS or Wii U software (or PS3, if that means anything).
I'd really appreciate any help I can get, because I didn't spend 10 dollars to play the single player missions, and as it is there's nothing left for me to do with this game - all the subs left to unlock are online. So I'm kinda stuck with a dud game until this gets fixed.