It has come to light via comments on my recent Google+ post and a post by Ingression, that the nature of Ingress Passcodes may have changed. It appears that passcodes are now limited in use, most likely to decrease the dilution of the game due to passcode lists like the Passcode Database on this site and the Google Doc that has been floating around.
I had the intention of adding to the database information about how each passcode was discovered to help players learn how to discover passcodes on their own within the media that is leaked into the game. Looks like this new feature will be in pretty high demand. It is unclear however, how limited passcode usage will become and if they will release passcodes more often or make the ones that are released more valuable, making the game more challenging. One possibility, is that you might need to have acquired the media in your inventory that the passcode was discovered in, in order to use it. When we determine answers to these questions, I will post them here.
In the meantime, I will get to work on expanding upon the Passcode Database to include information on how each passcode was discovered to better equip players for when they do discover new media, so that they can make use of any secrets hidden within.
For now, keep up the good fight and stay safe out there!-lunger