Hello, I was just helping my younger brother transfer his old 3ds data to his new 3ds. We did everything I did when I was able to sucessfully transfer data, but something went wrong for him. We were transfering using the pc method, and everything was going fine up until the point when he needed to transfer SD card data via the pc. It seemed like we were able to sucessfully transfer all of his internal memory, but for some reason his new 3ds wasn't able to access SD card data. All of his folders and things like play coins and miis that are tied to the system memory are all there, but all the games he downloaded are missing. It seems like the system internal memory successfully transfered, but SD card data did not. His new 3ds appears to be having issues reading the SD card data, so we suspect something went wrong while transfering data to the SD card. It's worth mentioning that the micro SD card adapter that we used was of a different brand than the micro SD card included in the system, although I don't think that would be a problem. I'm guessing its either the SD card data isn't formatted correctly, his New 3ds is broken and can't read SD card data, or the SD card included with the system is broken. All his SD card data isn't gone, its backed up on his desktop, so this should still be salvagable.
Any advice on what could have gone wrong is much appreciated. Once again, he followed the exact steps I followed and I was able to sucessfully transfer all my data.
Its also worth mentioning that he opened mii maker after the process failed, which created some extra SD card data. I hope this won't be a problem.
.