If Vac was unable to verify the game session error appears
on CS: Go then you are not alone. Most of the CS: Go players get the error when they were trying to match make. It is the difficult situation for the players when they do not able to match make. Now you do not need to worry as this error can be fixed in simple steps. We are providing here the solutions to fix this issue.
Method: 1- Verify Game Files

The integrity issues with the CS: Go game files may create this issue. If you want to get rid of this problem then you must check game files with steam client. To do this task, look at these steps and perform them on your game.
Method: 2- Restart your steam client
The issue may happen due to problem in steam client. This problem could arise at the beginning of steam client. So it is better to restart the steam client. Here are the steps to follow.
Method: 3- Repair steam client
If restarting the steam client isn’t working on your game then it is better to repair the steam client. Users who do not know how to do this procedure must follow the steps provided here.
"C:\Program Files (x86)\Steam\bin\SteamService.exe" /repair
If your game file is on different location then change the address.
5. The procedure may take some time so wait for the process to end. Then run your steam client and launch the game and check if the
error is fixed.

Method: 4- Update the drivers

The drivers in your device may create the problem for you. So you are recommended to update the drivers. This procedure can be done in two ways that is manually or automatically. Everything depends on how you want to deal with the issue. Here we are providing the steps to perform this task manually.
  1. Go to Settings > Update and Security.
  2. Click on the Check updates option and wait for the processing to end.
  3. Go to Control Panel > hardware & Sound > Device manager.
  4. You will get the faulty driver with a yellow sign or the driver related to your game. Now Right click on the hardware and select Update driver software. Also do not forget to check the audio drivers, another party webcam or other drivers.

Conclusion

The errors which occur at the time of playing games are irritating. But there is no way to ignore them. Many issues become big when we ignore small issues in our device. Well, in the VAC was unable to verify game session, some of the solutions are suitable. You can remove the error by using these methods. Anyone can use these solutions to remove the issue. If you have query related to these methods then without any hesitation leave your message in comment section.