If you actually need a legitimate activation key, you’ll need to purchase the game from an official store like Steam. The current version on Steam is often more up-to-date than 1.6.1, but older versions might be available through official backup copies if you already own a license.
If you are looking for an activation key for Scania Truck Driving Simulator (v1.6.1) Scania Truck Driving Simulator 1.6.1 Activation Key
The wheel spun. The screen flickered.