Follow everyone else's advice and keep trying before you come to the following conclusion, but there's every chance that the method just isn't for you. Different people have different ways of getting lucid, some ways work for some, others work for others. That's just how it is, everybody's different. It isn't a bad thing, it just means experimentation is a big part in learning how to lucid dream; experimenting with methods, and various ways of doing those methods.

Good luck!