There's reports circulating that some codes for Alien: Isolation's pre-order content are not working on PlayStation 4. Creative Assembly are looking into it, and are hopeful that they'll be able to fix the issue for those who bought the Nostromo and Ripley editions of the game, and who are now struggling to access the two extra missions that star the original crew from the movie on which Isolation is sequel to.
Thanks, Videogamer.