Why some cars wont start?

The answer is not in the keys.  It is in the pairing of the keys and the starter button.  There are stories where cars dont want to start and mechanics have changed from all sensors to ocils and injectors.  Only for the scanner to show that something is wrong with the key programming.

So the first step really is to think electronic.  We need a sort of password or registration.   First step, have your electronic engine scanned.