I just re-read your original post, and you did say the light lights when you press the button on the remote. I missed that earlier. I assume you mean the light on the remote fob, not the light in the interior of the car. Can you confirm?
If you meant the light inside the red window on the fob, then the batteries should be fine, and the first part of my instructions can be skipped. I would think if you have the light working on the remote consistently, your remote has a good chance of actually working. So maybe it is just the programming part that isn't set up right (if you're lucky). Try the other part of the instructions about putting the key in the ignition first, THEN pressing the buttons, and turn the key. Maybe that will do the trick.