Hello Holotable Heroes,
We are aware of a bug that is causing a group of players to not have access to GAC.
The issue exists due to an incomplete PvE Battle, so if you force close the game during a PvE battle, your chances of lockout increase.
Start and finish a PvE battle prior to going into a GAC battle should workaround this lockout in the meantime.
We are actively looking for a fix of this issue.