Same happened with me, but i was using Monster Hunter XX.cia decrypted.
I was trying to patch the Dasding English v3 since there's will not be a better version by now and using Luma3DS to patch is slow to load on some parts, like viewing the guild cards.
Thanks! I used "HackingToolkit3DS(v9) a older one and worked, unpacked romfs to a folder.
But there's another problem to repack!
I have tried many times, do everything fine and the program say that is creating the cia BUT after some time the file it created is nowhere to be found, not even hidden file. maybe theres a bug or it send the created file somewhere else?
Thanks for you help anyway