If you try to get in a car park equipped with license plate reading, your license plate may not be recognised at the entrance (dirt, snow, faulty camera, etc.).
You can then use your vehicle's emergency code or QR code, depending on the car park's equipment.
The emergency keypad or QR code can be found in My Account, Vehicles, Open barrier.
If the automatic opening of the barrier does not work when you leave, use the same emergency code or QR code that you used to enter.