Did you update the usrcheat.dat or the cheat.dat?
I know that for using a usrcheat.dat it requires a EMPTY cheat.dat file.
Anyway like Narin said go to:
Extract and find: USRCHEAT.DAT replace this one with the one on your SD card.
If your cheat.dat file is not 0kb use the one from original firmware.
(1) The R4DS uses the cheat.dat and usrcheat.dat files. Use only one of these files, not both as using both can cause some cheats
not to show up.
For some reason I think you use both and 1 of them is Japanese.