Why is the car key unresponsive after replacing the battery?

[SanLeo]

After replacing the car key battery, it needs to be re-paired before it can be used. Below are specific instructions for car key replacement: 1. Re-pairing method: Insert the remote key, turn it to the "1" position, then quickly return it to the 0 position. Repeat this 4 times and swiftly remove the key. Press any button, such as the unlock button, for 4-5 seconds until you hear a sound from inside the car. The key coding is now complete. 2. Smart key principle: Smart keys can emit infrared signals to open one or two doors, the trunk, and the fuel filler cap, as well as operate the car's windows and sunroof. More advanced smart keys resemble credit cards; when the driver touches the door handle, the central locking system activates and sends a wireless query signal. After the smart key card responds correctly, the car lock automatically opens. The engine will only start when the central processor detects the key card inside the car.