You have to check all fuses and relays first before you start replacing things chasing the problem and spending $$$$$$$for the wrong reason was this the same issue before you changed the neutral safety switch yes/no? That switch has to be adjusted on most cars before it will start anyway go to your battery cables check for looseness that they are clean of sulfer/battery acid /corrosion around the terminals and post and that you can not turn them by twisting now go to the power distribution box and do the same thing under the hood there's a relay there that should click when you turn the key after the cleaning check that and make sure the cable connections to the box the stud and the cables lugs are clean and shiny also the ground to the engine and those starter cables I understand everything works but that's possible because a limited amount of voltage is needed for this components to operate also this could've happened if corrosion was present you could've lost power momentarily which would sound the alarm or the horn it would've put the car into theft mode if the remote keyfob was not used to stop it you have a pats system (secure a lock) from ford with a chip key any break in power will cause your vehicle to go into theft mode and you might not have known that it happened this will give you a totally dead key no click at all as well as the neutral safety switch same thing if not adjusted properly if that applies to your car you need to have someone turn the key to start while you are moving the switch to adjust it then it will crank,and remember that obviously I'm not there so I need you to be as precise as possible in your post of (a) symptoms before you changed any parts (b) all the things you did upto now and write it all down so you don't forget to include it in the next post we will get there good luck stephen