It is important to know that there is no official ISO for the PPSSPP emulator
No official GTA 5 ISO exists for the PPSSPP emulator, as Rockstar Games never released the title for PSP. Available "GTA 5 PPSSPP" files are unofficial fan-made mods, typically based on GTA: Vice City Stories Gta 5 Ppsspp Download Iso Zip File For Android