This error causes or prevents your account from successfully logging-in into the game from a number of different reasons such as connection and/or server issues and more. To be able to fix the issue please do the following;
- Basic trouble shooting, refer to the article Here if you want to know more.
- Check Brave Frontier's official channels such as Facebook and gumi's forums for any connection or server update. There maybe issues or current server maintenance on-going during the time that you are currently trying to log-in. For the official channels, you can refer Here.
If you found no problems both from your connection or issues in our side then please do try to perform Clear User Data. You can find the guide Here.