Open your and right-click on Call of Duty: Modern Warfare 3 . Select Properties > Local Files (or Installed Files ).
Navigate to your install folder: SteamLibrary\steamapps\common\Call of Duty Modern Warfare 3\zone\english (or your local language). Check if the file so_survival_mp_paris.ff exists. Mw3 Error Could Not Find Zone So Survival Mp Paris.ff
Do not panic. Follow these steps in order. The first solution fixes the issue for 80% of users. Open your and right-click on Call of Duty: Modern Warfare 3