Please confirm the form of the SD card firstly. It's supposed to be FAT32 or exFAT.
And replug the SD card and wipe the metal contact, pls.
Try to use the camera with other SD cards and other cables to see if it works.
（We advise you to use the SanDisk C10 SD card.）
And you should turn the camera on for connecting.
Please check the USB port and the connector of the cable to see if there is any obvious broken part.
Sometimes, the power supply of the usb port of the computer is not enough will cause this, too.
Pls try with the back port of the computer and other computers.