After the update of the Biohazard Catastrophe, the Tier 2 skills of all classes were no longer available. This was a common problem. As far as I know, this is because the game developers made some adjustments and modifications during the update, resulting in the disappearance or enhancement of certain skills. To be more specific, some Tier 2 Skills of certain classes had once been given powerful effects, but now these skills could no longer be used or were weakened. This could be due to the game's balance adjustment or other reasons. However, it is important to note that other changes may occur after the game update, so players are advised to continue to pay attention to the game's updates in order to better experience the game. If you have any other questions, please feel free to ask me.