Possible reasons why external disks are not displayed： 1.connection problem： •Make sure the cables are connected correctly。The USB or HDMI connection should be plugged securely into your Mac and external drive ports。 •Try changing to a different cable，To rule out the possibility of cable failure。 2.Port problem： •If you have multiple USB ports，Try connecting the external drive to another port，Check if it is displayed on the desktop。There may be a hardware problem with the currently connected port.。 3.System problem： •Restart your Mac，to clear possible temporary data corruption。Select Apple menu > Restart or hold the power button，Then press R key to restart。 •Reset NVRAM (Non-Volatile Random Access Memory Parameter Memory)...