Some online/RPG games don't allow you to attack monsters with 20 levels higher than the level of your characters because you will hit MISS again and again. It doesn't matter if you are powerful or have full stats if the level of the monster you attack is way higher. Once you reach a level close to 140, let's say 136-137, then you will have a possibility to inflict damage. This is a prevention implemented by the developer, because image that all low level players will attack high level monsters to grow faster since the XP given by those monsters will be way higher.