My external drive stopped showing up. I tried everything suggested by different users which included:
Use disk utility and try running First Aid, Mount, Eject.
User terminal and run command diskutil list, info, eject, mount
Restart mac
Try different USB cable
Try attaching the external drive to a different Mac
None of the above steps worked. I decided to use Windows and it rescued me in this situation where Mac was a total failure. I attached the external drive to only Windows laptop I had and it offered me to scan/fix errors on the drive. It worked like a charm. After fixing, it was successfully recognized by my MacBook and Mac Mini.