You have wireless communication on and still failed? In that case look up the titleID of the game on fbi, and you need to find the seed file online somewhere, and put it on a folder on the root of your sdcard SD:FBI/Seed/*put seed file here*.
Here : https://3ds.hacks.guide/region-changing
It says "Region changing using CTRTransfer (which this method uses) seems to cause reboot patches to break. The cause for this is unknown, but Old 3DS users, for now, will be unable to play extended memory mode games (such as Monster Hunter, Super Smash Bros, and Pokémon Sun / Moon) until they format their devices."