New refurbished Nikon S3100 with new SD card shows error code ("this card cannot be used".) It is the correct card, also. Any ideas?
There is a tab on the card that locks it from being written. Make sure that's not in the wrong position. Try moving it out of the lock position and see if it then works.
Otherwise try formatting it in camera, and if it won't format, try formatting the card on your computer using a card reader.