Game doesn't launch/crashing at startup possible fix

• 1. Game has basic antitampering protection, supposedly it blocks game startup if suspicious programs and services running in background are detected. You can see if it's the issue by starting windows without third party services and apps. Common offenders would be Nefarious service from DSX and WinDivert service from winws. Steps will be discussed below.
  
  
• 2. Game has various reasons to crash with startup, friend list being too much or hackers abusing game vulnerabilities to stop you from playing the game. I recommend running black ops 3 patch such as t7patch from https://github.com/shiversoftdev/t7patch to avoid possible game issues. Download latest version archive, unpack it in separate folder and run patch executable before the game, keep patch running during gameplay. You can follow video guides on how to run it with the game

Fastest way to determine if it's third party app is by booting without any apps and services using diagnostic startup option

Beware that this is an Advanced troubleshooting method and, although there's nothing dangerous with doing this, anything you do after this is UP TO YOU to figure out.

In order to get diagnostic startup, hold Windowsbutton+R to get Run window and type msconfig there, press OK

then choose diagnostic startup, ok and reboot as it asks to save changes.

This will be a one time thing, you will be able to boot normally after you check the game by choosing msconfig normal startup.

• Start Steam in Diagnostic Startup. If steam asks about installing service, then ignore it and don't install it, continue without installing its service, it won't be needed to launch the game.
  
• Launch the game from steam, patch is not required to check so you can do without it. If the game loads normally, then some app or service is interfering with game boot. You will have to find it by yourself by launching apps one by one with the game afterwards. In my case I found out that WinDivert was causing the issue, stopping the service itself with the app was enough to get game running.