Fix VAC Was Unable to Verify Your Game Session Error

Problem overview

When trying to queue for matchmaking in Counter-Strike 2, Team Fortress 2, or other Valve games, you get abruptly kicked with an error stating “VAC was unable to verify your game session”. This prevents you from playing on secure servers.

Common causes

• Corrupted game files or temporary cache files failing authentication
• Missing administrator privileges for the Steam Client Service
• Background software (like cheat engines or aggressive overlays) interfering with VAC
• Stale DNS cache or network connection issues

Solution 1: Verify game file integrity

1. Open your Steam library.
2. Right-click the game (e.g., Counter-Strike 2) and select Properties.
3. Go to the Installed Files tab.
4. Click Verify integrity of game files.
5. Wait for the scan to finish and let Steam redownload any corrupted files.

Solution 2: Restart the Steam Client Service

1. Close Steam entirely.
2. Press Win + R, type cmd, and press Ctrl + Shift + Enter to run as administrator.
3. Run the following command to stop the service:

   net stop "Steam Client Service"

4. Run the following command to start it again:

   net start "Steam Client Service"

5. Relaunch Steam and try joining a match.

Solution 3: Flush DNS and reset network settings

1. Open the Command Prompt as an administrator.
2. Enter the following commands one by one, pressing Enter after each:

   ipconfig /flushdns
   ipconfig /release
   ipconfig /renew
   netsh winsock reset

3. Restart your computer.