@Raphael > Nice meeting you on Reddit - thanks for popping over here.
So, first off, I'm gathering you downloaded rekordbox from here: http://rekordbox.com/download/download.php?lang=en
I'm just after seeing your screenshot and its very obvious whats wrong - rekordbox hasn't analysed any of your files.
See all those 0% progress bars? You need analyse all the tracks and the keys will then be detected.