in some cases, we will have VAC authentication errors when matching games. Generally, restarting step can solve this problem. In addition, you should pay attention to whether there is a "steam client service" process in your process. At this time, its CPU occupancy is very high (in general, it does not work). Close it, or even restart the game, because you may have just replaced your steam account, and this process is the service data of the last steam account, resulting in your game can not verify your steam identity, so that you can not play the game. In addition, VAC prohibits access to the security server is an error that can not be solved. One solution is to verify the integrity of the game in its attributes.