Why Won't My Computer Read My Camera Card?by James Clark ; Updated September 28, 2017
Digital cameras store images on memory cards. Many now use SD or SDHC cards, which are about the size of a postage stamp. The memory card can be extracted from the camera and inserted into a card reader for rapid transfer of the photographs to another device, such as a computer. Some computers also come with card-reading slots. Transferring photos to a computer lets you delete the images from the memory card, freeing it to record new shots. If your computer won't read the memory card, try troubleshooting the problem before replacing the card or taking equipment out for repairs.
Eject the memory card from the computer's card reader and inspect the card for evidence of physical damage. If the card is bent, cracked, chipped or otherwise visibly damaged, you might need a new card.
Turn over the memory card to check for a sliding lock switch on the underside. Slide the switch to the unlocked position and try the card again.
Insert the card into a different memory card reader to confirm whether the problem is the card, the reader or the computer. If the card still is not working, it probably must be replaced. If the card works in another device, continue troubleshooting the computer.
Push in the cable for an external card reader into the port on the computer to ensure you have a good connection.
Update the memory card drivers for your computer's operating system to ensure that your equipment is compatible with the card. Driver updates are available from computer manufacturers, typically for download at no cost. Restart the computer after any update to ensure the changes take effect.
Reformat the memory card if all other attempts to read the data are unsuccessful but there is no obvious sign of external damage to the card. It's possible that the data on the card is corrupted but the card still works. Insert the card in the card reader and right-click on the drive letter (such as E or F) for the reader. Highlight "Format" and press "Enter" to reformat the card. This will erase all data on the card, but it might let you continue using it.