[Solved] Unable to Initialize SteamAPI Error when launch Game from Steam Client

Problem: “Unable to Initialize SteamAPI” error prompt after click on the game from Steam library. This error may caused by firewall, Comodo Internet Security or Steam beta client.

Unable to Initialize Steam API Error

Content Summary

Solution 1: Add Exception list for related Game’s Executable in Firewall
Solution 2: Opt out of Steam Beta
Solution 3: Disable Auto-Containment on Comodo Internet Security
Solution 4: Reinstall Steam PC Client
Reference

Solution 1: Add Exception list for related Game’s Executable in Firewall

If you have third-party firewall active or Windows Defender Firewall turned on, it might be blocking the game’s executable from connecting to the Internet.

For Windows Firewall:

Step 1: Go to Start > Control Panel > Windows Firewall.

Step 2: Click Allow and app or feature through Windows Firewall option from the left side list of options.

Step 3: Locate the game’s entry on the list and check the boxes next to both Private and Public networks.

Step 4: Click OK and restart computer.

Solution 2: Opt out of Steam Beta

Step 1: Go to Start > Steam PC client.

Step 2: Click on Steam option > Settings > Account tab > Change button under Beta participation section.

Step 3: Click to open the drop-down menu, choose NOTE – Opt out of all beta programs option and Apply.

Step 4: Exit from Steam PC Client.

Step 5: Press Ctrl + Shift + Esc key combination to open Task Manager.

Step 6: Click on More detail, select Steam-related processes (such as Steam.exe, Steam Client Bootstrapper or GameOverlayUI.exe) one by one and choose the End task option.

Step 7: Locate Steam.exe executable and right click to open its properties.

Step 8: Go to Compatibility tab, check for Run this program as an administrator option and click Apply.

Step 9: Open Steam PC Client and try relaunching the game.

Solution 3: Disable Auto-Containment on Comodo Internet Security

Step 1: Open the Comodo Internet Security UI.

Step 2: Go to Settings > Security Settings > Advanced Protection > Containment > Auto-Containment.

Step 3: Uncheck Enable Auto-Containment option or locate the game’s executable from the list and turn off the slider under Enable Auto-containment option.

Step 4: Confirm the changes.

Solution 4: Reinstall Steam PC Client

Step 1: Open Steam Client.

Step 2: Go to Settings > Downloads > Steam Library Folders.

Step 3: Navigate to the file path stated in Steam Library Folders and find steamapps folder.

Step 4: Backup steamapps folder.

Step 5: Repeat the same process for all library folders.

Step 6: Go to Start > Control Panel > Uninstall a Program.

Step 7: Locate Steam entry on the list, click on it once.

Step 8: Click on Uninstall button and confirm any dialog boxes which may appear.

Step 9: Restart computer.

Step 10: Redownload Steam and run the downloaded executable on computer.

Step 11: Add the folders again as the Steam library folders.

Reference

Steam Community: [SOLVED] “Unable to Initialize Steam Api” After Latest Update
Community Beta for Bethesda.net: HELP-unable to initialize steam API error
Reddit r/Steam: How do you fix “unable to initialize steam api”?