Few things are more frustrating for a gamer than the anticipation of dropping into a classic multiplayer match, only to be met with a cryptic error message before the main menu even appears. For veterans of the Call of Duty franchise, the error in Modern Warfare 3 (2011) is infamous. It acts as a digital brick wall, preventing access to the campaign, Spec Ops, and multiplayer.
If you are playing a non-English version of the game (Russian, Polish, etc.) on an English Windows OS, the game might fail to load a specific character set. Call Of Duty Modern Warfare 3 Could Not Load Localization
Advanced users discovered a workaround that forces the game to bypass the corrupted localization loader by using command line arguments. This is particularly useful if the error occurs when switching between Single Player and Multiplayer. Few things are more frustrating for a gamer
Once completed, launch the game. In most cases, this solves the problem immediately. If you are playing a non-English version of
> Select game > Ensure all "Modern Warfare 3" components are checked and applied. Restore Licenses (PlayStation) Users and Accounts Restore Licenses