You only get that achievment if your belt rank is 1337. I'm assuming you got the new system's rank to be 1337, which is not the correct type for you to be able to earn the achievment. You can check your belt rank in-game by typing "/stats (your name)", and on the forums by looking at your gamer card. IF, however, you did infact get your belt rank to 1337, it should give you the achievment if you have the rank for over a day( or whenever the next day starts based off of the toribash site's date). In this case you will need to contact a Gm or something if the achievment isn't working.