OK, lets start from the begining. lets make sure you are doing correctly. the procedure for unlocking the radio as follows, you need to get a 6 digit code retrieved from radio then post me back this code, I will post you back a factory backup lock code that will enable you to punch this code in to unlock.
following these instructions, let me know what happens.
Press and hold push buttons 2 and 3 until a three digit code appears on the display.
Write the three digit code on a piece of paper.
Press the AM/FM push button, a three digit code will appear on the display again.
sorry we couldnt help, I wish I had ask from the start if this one the orginal radio. could have maybe save you some headaches.