For some reason, my Action Replay isn't working for my Nintendogs Dalmation and friends?!?

So the codes that you get when u buy the thing were already there and i was like alright lets go! yay! (i've already beat the game on another card so don't gimme that crap about ruining the game) so i restarted the game, got a german shepard, named him, taught him sit then i went and put in the action replay thing. So i start the game thinking every things nice and dandy but nooooo... it doesn't work?! so i go back futz around for a while and press select and stuff in the main menu and in the code area but nothin is workin? Why is that? I only want the 2 MEASLY CODES- CASH AND POINTS!!!!! please please tell me how to start it up properly.... thnx so much