I recently screwed up and re-wrote my WD 8 Tb external as an .iso. I have tried to restore it as a data drive without success. Solus no longer sees the drive -- though it does see the smaller Toshiba external. Nothing I try seems to have any effect. How do I recover this drive? I know the data is gone to data heaven, but I would like to use the drive again.

You will need an .iso to erase your .iso.
Assuming the bios is not nuked and you can boot the usb drive first.
"Data heaven"--I like that🙂---I've sent a lot of drives there!

Maybe I'm wrong, but I would think you just have to repartition it and reformat it.

The difficulty I'm having is that the operating system doesn't recognize the drive, so I can't write to it with anything, let alone an .iso. I'd love to go to heaven to get the data back, but the return trip might be a problem. Thanks for the response, by the way.

Should work using gparted and follow dbarron post.

In gparted, create a new partition table on it. Under Device > Create Partition Table.