Read the instructions. The ROM must be re-encrypted on a 3DS with Decrypt9 to work with Gateway, zero-key encryption (or decrypted .3DS files) doesn't work.
Also bad news , if you want to play Nova or Umbra online , DON't use cias, that goes for any cia that goes online, I am sure that Nintendo caught all of those people using Pokemon Sun or Moon online, not through playing online early but through the tickets and going online early, but they still know who is using cias online, I now know that cias ALWAYS create bad tickets and I am sure that the tickets are sent off while playing online with millions of people playing online ip addresses would be too hard to track, but bad tickets are easy, either they are good or they are bad , its that simple. And importing a good ticket will not overwite a bad ticket, that too I have found out, thus if you have a cia and you are online guess what your ticket will be flagged as not legitimate... if you really want to play online and like the game the buy it. That is the only way to play online and not set up red flags to Nintendo. For hacks if you have an original cartridge or eshop title, use them and the saltysd version, I am NOT supporting online use of cias in any form I can prove this when using a cia and deleteing it, then trying to download it from the eshop sure it says that you have already downloaded it, and at 99 % you get the dreaded 6016 error, that is not about an error on your sd card but its about using a bad ticket and using a cia from Nova or Umbra and tehn trying to download your original cia from eshop as many do just to test cias , guess what the ticket from your cia is bad and even the legit ticket that they send you DOES NOT overwrite your Sun or Moon bad ticket.the only way to download a legitimate file is to delete the ticket, you can do that google it....dont ask me how to delete a bad ticket until I get permission to tell you how.... 3DS files on the Gateway are the same, bad tickets...rcamp48
PS: For those of you who want cias for randomized versions, I have found a way of creating the randomized part and when the file goes to create the cia I halt the batch file , it then writes the randomized version to the a\0\8 folder , 2 for Nova , 3 for Umbra.... I can upload customs versions with only those files , you copy them into your Nova saltysd a\0\8 folder or Umbra saltysd a\0\8 folder and if you have a legitimate game of sun or moon (eshop or cartridge)....you can probably go online safely. (If youhave not edited your Pokemon , I think randomizing them is different but I would probably use a randomised version offline as what I have done to mine is reandomized all pokemon caught, and randomized all moves learned at certain levels, also masterballs sell for 50 bucks...if I get Dio's permission I will upload only the 2 or 3 file....rcamp48