After Partitioning 8TB Drive, Drive will not mount

I re-purposed a Seagate HD from an external drive as a backup for the 4th slot on my MacPro. It had been working flawlessly, but I wanted to use it for both CCC (Carbon Copy Cloner) and Time Machine. Shortly, thereafter, and despite some warnings from the OS, it would no longer be addressable.

I tried all of my utilities to erase, reformat, etc., but nothing seems to work. I don’t think that there’s anything really physically wrong with the drive.

Suggestions?