1996 Nissan Maxima Not able to turn key in ignition

Your key could be worn out.
Or
the pins in the lock get dirty and stop moving freely.
You can try this.
Insert the key all the way in to the lock and then tap the head of the key with a small hammer, the handle of a screw driver, your kid's MP3 player.
Whatever you have handy.

Or removed the lock from the steering wheel and rinse it out by spraying brake cleaner in to it.