Theory Of Operation
WARNING: This page is about a different car, the 2015 Fiat 500. However, it is still accessible from the selected car via links, so may be relevant.
The RKE (Remote Keyless Entry) Fob can be the right one for the vehicle but if the customer wants, he can have the dealer delete a key. It may be the one that was lost. Once it is deleted, it cannot be activated again.