Retail cartridges work but you must own a Action Replay DS(i) device in order for retail games to work online. You use the program called WfcReplay v0.5.Does this mean retail cartridges don't work?
With a copy of the game you drag and drop the ROM file onto WfcReplay.exe,
then it will make a code that you can use for the action replay ds(i) to allow the game to be played online.