Initially, Anno 2070 used (a third-party DRM) combined with a mandatory Ubisoft login. This meant:

If the game continues to ask for a key or says it is "already in use," try these official steps from Ubisoft Support:

Anno 2070 is a solid real-time strategy game that offers a rich and engaging gameplay experience. While it may have some drawbacks, the game's strengths make it a great choice for fans of city-building, economic management, and strategy games.

If you have lost your key and have proof of purchase, the best course of action is to contact Ubisoft Support to recover your account access. Are you having trouble activating a specific copy of the game, or are you looking for help with a "Key in use" error

Finding the serial number or activation key for is a common step required to register the game during installation or to unlock specific downloadable content (DLC) like Deep Ocean . Because the game uses older Digital Rights Management (DRM) systems, you often need to manually input these keys even after the game appears in your digital library. Where to Find Your Anno 2070 Serial Number