This question is an exact duplicate of:
I am unable to mount my WD Easy Store 4TB on my Mac. I am using macOS Mojave - 10.14.5. I tried several commands using terminal to unmount, but all in vain. It shows ejected but still shows in distutil list and disk utility.
I tried using the hard disk on windows pc as well, but it just doesn't read there.
Suggest me ways to rectify it and save my data.