If your tool interacts with Steam API:
The "steam_api64.dll missing" error in typically happens when your antivirus incorrectly flags the file as a threat or when game files become corrupted during an update. Because this file is essential for the game to communicate with the Steam client for achievements and user authentication, its absence prevents the game from launching entirely. 1. Verify Integrity of Game Files (Recommended) Call Of Duty Black Ops 3 Steam-api64.dll Missing
Before giving up, ask yourself:
& "C:\Program Files (x86)\Steam\bin\steamservice.exe" /repair If your tool interacts with Steam API: The "steam_api64