Action Replay (DS/DSi/3DS/Wii/PS2/GameCube) losing its code database is common. Here's the recovery ladder:
ARCodeManager.exe for DS/DSi; AR_MAX for PS2)..xml / .codelist for your game/region./codes/ folder on SD/USB → re-download.If hardware dead: replace. Datel (manufacturer) no longer sells/supports. Buy used working unit + flash community DB yourself.
Using AR on online games (Mario Kart DS, Pokemon, Animal Crossing) risks permanent Nintendo Wi-Fi / Nintendo Network ban (error 20100 / 20101). Use offline only.