If one of the remote control keys1 has been left in the car then the keyless functions are deactivated in case the car is e.g. locked with the other remote control key that belongs to the car. This prevents unauthorised entry.
The next time the car is unlocked with the other remote control key the forgotten remote control key is reactivated again.
Important
Avoid leaving the remote control key with PCC behind in the car. If someone breaks into your car and takes the remote control key, it will e.g. be possible to start the car by pressing the remote control key in the ignition switch and then pressing the START/STOP ENGINE button.