Drive won't mount

WD External Drives WD Portable Drives
1

I am trying to mount an EASYSTORE external on an
iMac OS/El Capitan/10.11.6
Will not mount on desktop.

  1. I have tried to mount through DISK UTILITY
  2. I have changed ports/cables

When I try to erase the drive I’m receiving the message:

Unmounting disk
Unable to write to the last block of the device
operation failled…

Any help would be greatly appreciated.