Sorry for the inconvenience : Steam is having some troubles right now since it's maintenance day. The game doesn't have any offline mode so it tends to go down when Steam does. If you run into this again, you can check if you are online on Steam and restart your Steam Clients.
i had the "anti cheat violation" kick last night when i selected commander class from demolitions
i doubt that was the cause but i still cant figure out what caused it ive only got the standard windows defender
i had to restart pc to be able to sign in to the game again as normal