Cwcheats are not working in any game

[LunaMoo]

If you talk about cheats made for PSP, making sure you have codes for correct version of the game while obviously important since even updates break it, just isn't enough.
PPSSPP by default allows games to use more memory which can improve compatibility in problematic games and allows for some cool stuff/hackish things which could require more memory than psp allowed, this however makes most simple cheats that just patch some variables in memory end up with different address on emulator vs real hardware which effectively breaks them. To change it, you have to open ppsspp system settings and change psp mode to psp-1000.

Even after doing so there will still be games for which PSP cheats will not work because emulation is imperfect and memory still differs from real hardware, that might never be easy to fix and the only thing we can do for such games right now is to create or at least port cheats specially for ppsspp.
In case you have games like that and can't create your own cheats nor port other people cheats, you can always check if someone already posted cheats working on PPSSPP or request such in "Codes Requests Thread".