This is a very annoying problem. You can’t play your game because of this error. You may not know how to fix it, and you may not even know what the missing file is!
Below is an explanation of the missing file and some solutions that have helped many other Steam users recover the missing file.
What causes Steam_api64.dll to be missing?
You might have accidentally deleted the steam_api64.dll file, or the file was corrupted or misconfigured by malware installed on your computer. This problem could be caused by corrupted or missing files related to the game, which causes DLL errors, some temporary game crashes, and some other problems on your Windows computer.