Select MW3 > Click the Options (gear icon) > Scan and Repair .
) for the introduction's script. If that folder is empty or the file is damaged, the engine fails to initialize the "Intro" zone, essentially leaving the game with no instructions on how to load the first cinematic. The Player Experience: Modern Warfare 3 Could Not Find Zone Sp Intro Ff
Modern Warfare 3 is split into "packs." You might have the launcher installed but not the actual Campaign files. Go to the Manage Files menu in-game. Ensure Campaign is fully checked and installed. Select MW3 > Click the Options (gear icon) > Scan and Repair