It may take some time before you realize the effects of your time using the paraliminal tapes, however, they are working for you each and every time you use them.
The reason people fall asleep when using PL tapes has to do our habits. The first thing we do when we go to sleep for the night is to relax before falling asleep. Therefore, we need to teach ourselves to remain awake while fully relaxed. When people first start doing meditation they have trouble staying awake, but with practice they learn to stay awake and fully alert. You can use the PL tapes to help you with this. Sit in comfortable chair and when your head drops it will wake you up. Give yourself a break here as you are training your brain to stay awake while being completely relaxed. Your success will come with time and practice. I am sure you will be delight with your accomplishment.