2004 Ford Crown Victoria Key won't turn

The first thing to do is try to free up the tumblers in the ignition lock cylinder. You can try some spray lubricant or graphite to see iot it will work. If it doesn't help, the key cylinder is easily replaced. Let us know. You will have 2 keys unless you have a locksmith key the new cylinder to your old key.

Remove the ignition switch lock cylinder
Insert the ignition key into the ignition switch lock cylinder and turn to the RUN position.
Push the ignition switch lock cylinder release tab (2)underside of the column with a punch while pulling out the ignition switch lock cylinder.