I admit, at first I thought it was the drive, but after a bit of research, this appears to be a thing, especially with Western Digital HDDs. The fix, I was told, was to plug the drive into a Windows machine, and if that machine could see it, it was fixed. That didn't work. 2/

The Windows machine saw the drive, and all the files, just fine. But my own machine still doesn't see it. What do? /fin