You're playing a secured copy of the game that has a protection script running in it to prevent you from gaining experience, and therefore, not playing through the game.
- Playing a game copy on a DS that aren't from the same region.
- Playing via ROM on an emulator.
Someone may've bugged out a copy and modded it just to screw with the players, as well. Either way, it's a security script, and likely won't be fixed.