Steam’s default folder has stricter permissions and different registry keys. Follow this alternative:
Among the pantheon of great mods, one name stands out for American realism fans:
Los Angeles (LA) Mod Emergency 4: Global Fighters for Life (also known as 911: First Responders
Released in 2006, Emergency 4 (known as 911: First Responders in North America) remains the gold standard for real-time strategy simulation in the emergency services genre. While the base game is set in a generic European city, the modding community has kept it alive for nearly two decades.
You must have or 911: First Responders (US version) .