Why won't my key turn all the way to "start"?

your ignition lock has to 'start positions", Key on and Start. If you can turn the key to the start position and there is nor response from the starter, you may have issues with the Transmission Range sensor, gear shift cable, wiring or Powertrain Control Module (PCM). Try this first, apply parking brake, depress brake pedal, move shifter many times from Park to 1st and back, then to park and try to start the engine. Sometimes the contacts on the Transmission Range sensor are intermittent. If that doesn't work, further diagnosis is needed. I recommend you go to your local dealership.

I guarantee what it is. At the bottom of the ignition switch it breaks off. And the contact plastic cannot push through I to module. Take out the ignition. Buy a used one replace the metal hardware while keeping your key and ignition. Reassemble and reinstall and and bingo you are rolling again. That's only when it won't start and you think it's starter