Go to C:\Users\[YourUserName]\AppData\Roaming\Sports Interactive\Football Manager 2010\ and delete the cache folder. This step forces the game to rebuild the language index.
FM 2010 is old. On Windows 10/11, you may need compatibility mode. Follow this guide exactly. fm 2010 language pack 9 languages repack
Football Manager 2010 originally shipped with full support for only (and sometimes a second language like French, depending on the retail region). The “9 Languages Repack” is a fan-made patch that adds official or community-translated text for 9 different languages into the game. It was popular among players who bought a version of FM2010 that lacked their native tongue. fm 2010 language pack 9 languages repack