Antivirus ESET NOD locks a file steamclient.dll, which is an emulator of the steam. Disabling antivirus does not solve the problem. Steamclient.dll file is removed when you installing or downloading CS: GO and CS: S.
Because of this error: “FATAL ERROR: Failed to connect with local Steam Client process!” when you start CS GO or CS Source:
Two ways to fix this:
First method.
1. Open ESET NOD. Select menu “Setup” and click on “Advanced setup“.
2. In the window advanced setup select tab “ANTIVIRUS” > “BASIC” > “EXCEPTIONS” and click on “Edit”.
3. Press “Add” and specify the path to folder CS GO.
4. Again, go to the main menu ESET. Select menu “Setup”, press on “Network protection” and disable “Personal firewall“.
5. Start cs go launcher and click button “Check and Update“.