We also receive this type of error and I know this is really frustrating, but after investigating the cause of this, the error is caused by the internet connection. We should always check our connection stability and make sure that no one blocking on your household.
Bull. This has been an issue since day 1 of the North American release of PSO2. I took a break from the game for 6 months and come back to find the issue still persists. You can't seriously think that it's on the player's end after all this time?
Also, as a note; I can stay logged into PSO2 JP for a solid 12+ hours. I'm lucky to get an hour or two in NA.