Time Machine disk not mounting
I am having issues with a Time Machine disc. I I try to select it and get asked to Erase (which I confirm) it then fails telling me that it can't unmount the disc. Then a few minutes later get an error message saying that the disc was ejected improperly. I could run First Aid on the drive OK. But now it won't even mount.
If I run Terminal, diskutil list I can see the drive and yet it won't appear in the main GUI DiskUtil interface. I have tried another cable.
iMac, OS X 10.11