The icon disappears when the sd card has no data/isnt inserted.I am 100% sure. The icon isn't there, and there is a micro SD in. I tried with and without a micro sd, and it isn't there.
Are you sure the correct firmware is on the micro sd cards?No, this is no simple problem. I know that for some flashcards that won't show the icon unless the micro SD is in. I tried multiple micro SD cards, and the problem never happened until an anticlone showed up on my flashcard.
If it is, you can install NTRBoot onto a 3DS, then use that to flash the original firmware back to the card. (if you can find the firmware*)The original firmware is back, but I actually do believe that it is possible for this card to be NTR boot compatible.