hi, i'm a korean steam user. I played multiplayer without any problems. However, suddenly this phrase starts from one moment and does not play co-op. 'You can not join the VAC security game session because it is not in normal authentication status.' I am a regular steam user, I have never used illegal programs, I have never used unusual items from illegal program users. I thought it was a simple mistake, but I have not played co-op for a few days. What is the problem and how can I solve it? I am very frustrated because I can not play co-op. My Steam account name is 'deepdarkdragon', and My steam nickname is '「空白」' Please solve the problem. ps. I played co-op with VAC security turned on normally.