What is the reason why a newly paired car key cannot start the car?

[LondonFitz]

Newly paired car keys failing to start the car are usually caused by steering wheel lock or ignition lock cylinder malfunction. Steering Wheel Lock: The steering wheel locks when turned after engine shutdown, as most modern vehicles come with anti-theft features. To resolve this, pull the steering wheel with one hand while simultaneously turning the key with the other. If unsuccessful, seek assistance from someone stronger. Ignition Lock Cylinder Malfunction: When the steering wheel isn't locked but the key still won't turn, the lock cylinder may be rusted. Try using lock cylinder lubricant. If ineffective, consult an automotive locksmith to repair or replace the lock cylinder.