External hard disks and pen drives connected via USB no longer show up in Finder.
What could be the possible reason, and how do I resolve this issue?
I have had this issue, on my 2017 MacBook Pro (2 USB-C ports) - and I found that the problem is resolved by resetting the Mac's System Management Controller (SMC).
Power your machine down, wait a couple of seconds - then press the left-hand side Shift-Control-Option at the same time, as well as the power button, for 10 seconds (I count slowly, so more likely 15 seconds when I do it). Release the keys and then power your machine back on.
Hopefully it will now register the external drives.
Have you tried to:
Does your Hard Drive and USB drive work on another Windows and Mac computers? Perhaps your ports are broken
Try to run these command from Terminal to see if the operating system is able to see your drives:
Launch Terminal.app and run the following:
cd /Volumes ls
Try to see if you see your drives here.
If you do see them, then run:
diskutil info "disc#"
diskutil eject "disc#"
Then run list again. When sure it's removed, then physically remove, wait a few seconds and reinstall.
If the issue isn't resolved yet, launch Console.app Then open and go to the Errors tab, plug your drive in and see if there's any red tags popping up which could help you track down the problem.
Try visiting an Apple Store and seek assistance with a Genius, if none of the previous approaches worked.