My sd card in the sd slot is not recognized by nintendo dsi? why?

pls help me. im using a sd card 8gb but it doesnt recognized by the ndsi but im very sure that my sd card is working well. can anyone help me?

It may be a contact issue, place a folded piece of paper to make the flashcart a slightly tighter fit into the DSi, taking care not to force it too much

Maybe you put it in the wrong way around :P

Is it recognized by any other devices?

Try reformatting it if you can.
It should be fat32.