I received my R4 Dual Core 2013 today and it worked perfectly. After I put the microSD in the computer and back in the R4 Dual Core 2013 my card was suddenly not detected on my Nintendo 3DS. I tried on another and it also wouldn't work. Tried it on a DS Lite, also not detected. Tried other microSD cards with the same firmware, didn't work. Tried another R4 Dual Core 2013 with the same firmware and microSD in the same 3DS I own, it WORKED. So there must be something wrong with the card (not with the microSD or the 3DS). Could my card be bricked? Or is it damaged (which would be very weird, because when the microSD was in the computer, I left the card on the table and didn't damage it all)? My card is exactly like this: My 3DS is on version 5.1.0-11E.