The key often won't turn in the ignition for several reasons including:  1. If you don't use the right key or use a different key  2. If the steering wheel gets locked. Turn on the ignition steering wheel and turn on the ignition switch.  3. Then turn the steering wheel smoothly. Do it carefully unless the steering mechanism hampers  4. If all the steps won't work for you, you better contact a 5. 5. 5. Toyota dealership to get your problem solved.