i guess your way of load game is wrong. in usb hdd GAMEZ/BLUS00974/PS3_GAME/ inside have param sfo and USRDIR file which is eboot inside. you can try like that. maybe you setup or install game way wrong. just check up other games folder. inside how other does installed. maybe then it will work.
Blus00974 is conan games's id number. Each game has their own id. You can see all games id number in param .sfo file that you can open by text editor and can see it end of the file. You can write name of game like conan-blus00974 or blus00974-conan. Then you know game id also you know game id number. As you write you have put game files more file inside.
After gamez folder isndie just put game folder no need to open usrdir file and again put game files. Just now i have wrote upside. Just try it.