This error usually occurs when trying to link a Steam purchase to the EA App.

Depending on how you purchased the game, your serial number is located in one of three places:

Without a valid serial number, you won't be able to play Need for Speed: Shift 2 Unleashed. The game will prompt you to enter a serial number during installation, and if you don't have one, you'll be unable to proceed. Having a valid serial number ensures that you can enjoy the game without any restrictions.

. If you reinstall the game or upgrade your hardware five times without first de-authorizing the previous installation, the serial number will be locked. Steam Community