First off, dry spells in both LD’s and dream recall do happen, so try not to get too frustrated. First thing to check is that your alarm is set for 90 minutes intervals after you go to sleep, with the first interval coming no sooner than 4.5 hours into sleep. Second thing to worry about is how much sleep are you getting, anything less than six hours is terrible from most dreaming work, and 9+ is ideal. The reason is that REM period length drastically increases towards the end of the night. Third thing is are you telling yourself when you’re going to bed that you’re going to remember your dreams and write them down, or something of the sort. As you do, you should be thoughtfully considering the meaning of the words, a mindless mantra is no good at all. Finally, as soon as you wake up, don’t move; just lie there and see what comes to you. Even if you don’t remember a full dream, do you remember a fragment, some details, ot even just a mood or impression you’re left with. If so, write it down. Try not to move until you’ve recalled as much as you think you’re going to then go right it down.
Also, we have a nice guide already compiled on the subject that you might want to take a look at here: [Improving Dream Recall)