Re: : sd card samsung GT-S7560M says no card
Plug the card into a card reader and plug the card reader into a PC. If the PC sees the card, there's a problem with the phone. If the PC doesn't see the card, run Computer Management/Storage/Disk Management, and see if the card shows up. If it doesn't, the card is bad. If it does, see if you can format it. If you can't the card is bad.
If the card is bad and it's a SanDisk card, go to
SanDisk microSD Tech Support, open a live chat (upper right part of the screen) and they'll replace it for you. If it's not a SanDisk you'll probably have to buy another one.