built-in keyboard and trackpad option not showing in preferences

Two weeks ago I turned on my MacBook Air the built-in keyboard and trackpad wasn't working! I have an USB keyboard and a magic mouse connected now to the system so I could still use it.

I went to the system preferences but for some strange reason the option ignore built-in keyboard and trackpad when bla bla bla .... is not available.

I've already reset SMC and NVRAM, battery is ok...

By the way when the system boots up the keyboard works but then it immediately stops working.

I've already ran the option+d combination and the test shows no errors.

This is an image of my system preferences / accesibility / mouse & trackpad

MacBookAir6,2 (A1466)