If the camera is available, most of the cards are good, and it is possible that
1. Your data cable or connection port is broken.
Try replacing a data line or read it with a reader.
2. Online USB port voltage is insufficient
Do not use the USB port on the front panel of the computer and try the rear USB port.
3. Computer system failure
Change a computer to try or reload the operating system
4. Incorrect operation
Some brands of camera and computer online operation setup is more troublesome (such as canon), should be the camera to the viewing file and then online. It is recommended that you read the manual carefully again.