Time Machine can't see My Book Live Duo :(

My Book Live Duo. MacBookPro OS 10.13.6

I have the My Book plugged into the router, my computer is connected to the same router wirelessly.

IN the Finder, I can see the My Book, can read the files on the disk, no problem.

However, Time Machine cannot see the disk. I have set it a Share in the Dashboard and designated it as Time Machine accessible. But it still cannot see the drive.

Any additional thoughts?