It pops up as soon as I’m logged into the game at character selection.
Sometimes it lets me click on and go to character screen but that’s it. Sometimes it kicks me out to login screen.
Launcher up to date. Game up to date. Started happening today for me.
A lil help here please. Not a pressing issue for me but any help appreciated with this warning window. 
same here every time Blizzard works on game lately things get worse.
I was having the same issue. Tried restarting launcher a few times but made no difference.
I did finally manage to get in game though.
If it lets you through to the character select screen, just click cancel a couple of times, then the game should let you in.
Hope this works for you guys too
I’m getting the same code - have rebooted etc. and still occurring.
same mhere and i dont know how to fix this
It’s called Maintenance.
Even when you manage to get into the game, the error is popping up as soon as you kill the rg for some reason, also in character select or game mode change.
Also none of the other problems were fixed. Everyone still showing as non season on my friends list.
This is still going on 2 hours after the maintenance window closed and no word from Blizzard?? At least tell us what is going on and an ETA on when the issue will go away.
The game is still in beta, give it some time… Not like its been out since 2008 or anything
Getting same error as OP. This problem is not occurring on Euro servers. How did Blizz manage to stuff up a simple server restart??
I’m in IT and maintenance issues can occur for many reasons. I don’t fault Blizzard for technical screwups. That happens. What I do fault them for is the total silence for more than 4 hours that there is an issue. They need to communicate better. They screwed up the server restart. I get that and it’s excusable. But going on silent running is not excusable. This is the core of Blizzard’s problems with customer relations. They don’t communicate and are too ready to blame the customer for any issue that occurs.
There has been ongoing issues for weeks that they haven’t fixed and EVERY maintenance so far has only made the game more broken. Interested if you fault them for that too? I do.
Oh kool, I’m now able to get into the game. I’m not sure what was going on but up until now I was having the same issue. Oh well. Glad w/ever was going on was fixed.