my 2000 mercury cougar 2.5 v6 has fuel and fire it still wont start it will crank but not start. i put a crankshaft sensor and a camshaft sensor it still wont start. what can it be

Yes could be the Anti theft. You can try to remove positive cable from battery and turn the key to start for one minute. Reconnect battery, this may reset your alarm depending on the problem.

If the battery was off of the car for some period of time or a dead battery long enough for the internal memory on the computer to die. That will also cause the car to go into theft mode You will have to get the computer reprogrammed call pop a lock and their guys have the program to install soft ware are you an buy the program but it's quite expensive.