Follow these steps to fix the problem.
- Check the SD card capacity supported by the device.
- Remove the card and reinsert to make sure it is inserted properly.
- Did you format the card with the same device? If you formatted with a different device, format the card with the device with which you want to use the card.
- Insert the card into another device and check whether the device recognizes the card. If it does, then the card is working. Refer to the specifications of your device for compatibility with the card.