Try this if the above fixes don't work.
I was getting this consistently when logging into the pvp NA server. I tried the Pve server, and it worked. So then I wondered if maybe it was the character data or something - because I didn't actually get in a few times and was wondering if that's what was wrong.
So I went to.
STEAM\SteamApps\common\ATLAS\ShooterGame\Saved\LocalProfiles
And deleted the profiles.
Don't worry, the actual character data isn't stored on your machine (because of cheating) this is just a cache type of thing.
Fixed the fatal error when trying to join a server.