Sometimes security software blocks the activation window from communicating with the server. If you'd like, I can help you with: Finding the official support link for key recovery. Comparing the system requirements for the latest version.
Open the game; a window will appear showing your unique Product Code.
City Car Driving uses a specific serial number system to prevent unauthorized use. When you purchase the game, you receive a serial number. This number, combined with your unique "Product Code" (generated by your computer's hardware ID), is used on the official activation server to produce an Activation Key.
Buy the game from the official City Car Driving website.
Check your email for the serial number sent after purchase.