When a lock gets worn, or a door has become unaligned the locks can become stiff, this in turn can cause the failure of a key in the lock, or someone may have inserted the wrong key, when this happens the lock will not work, in most cases I can remove the damaged key from the lock, and then check the door alignment, and check the door lock for damage.
If the door needs adjustment, I am able to re align the door, and check all functions of the mechanism.
If the door lock is worn or damaged I can offer a replacement service.