1. Check that the SD card is properly inserted in the SD card slot.
2. Try shutting down and restarting your device.
3. Make sure that the device recognizes other types of cards and media.
4. Back up data if possible before attempting further repair or software fixes.
5. Try to scan your device for errors or viruses using a reliable antivirus software.
6. Perform a master reset on your device as a last recourse.