In case you encounter Error 406 when trying to log into Guardian Tales, please try the following steps:

• Open Guardian Tales and Connect your account.
• Change the server to a different one than the one you usually connect to (for example, if you are playing on Europe, try selecting Latin America server). 
• Upon changing the server, the game will ask you to restart, so restart the game and open it again. 
• Once you open the game again, change the server once again back to your original server and try logging in again.