The file should work, as many people have used it at this point. Make sure that:
1. You have the most current version of the game.
2. You do not have the game on your system drive (the one Windows is installed on), an external/usb drive, or an especially deep directory structure (folder inside a folder inside a folder inside a-) as these can create issues occasionally.
3. Try restarting the game and retrying a few times. If this doesn't help, try a full "fresh install" by extracting the zip in a new place, copying over your save files (and Datacrystal file if needed) and moving the gallery unlock file into place on THIS new install.
4. And of course, double-check you're moving the unlock to the right place: js\plugins. You can also just open the Gallery file in js\plugins to check, it's just a text file. Everything in '' should be a 1, 0s represent locked gallery entries. If you see zeros, you did something wrong. You can edit the file directly, but be sure to ONLY change 0s to 1s: added spacing or other characters will break the file.
5. If none of this helps let me know. It is possible I've changed something in an update that broke this somehow, though I don't think this is the case.