According to the news, Nintendo 3DS update the firmware to v4.2.0-9 today. You can use the system update to update your console to the newest version. And unfortunately, almost all the flash cards get banned. I just test the flash cards i have, dstwo, ak2i. TTi, M3 can't work, r4i gold 3ds( r4ids.cn ) work. i just have one card worked. Good job r4i gold 3ds!
now,more and more cards can work well on 3DS V4.2.0-9,such as Ace3DS PLUS,r4isdhc 3ds,r4itt3ds and so on.I have tested Ace3DS PLUS on my V4.2,works perfectly ,it directly compatibility without any updating needed.