I ran Nautilus with root privileges, same error message. I will read about FUSE support, though, thanks.
GUI is the default Gnome file manager (Nautilus).
When I create 2TB It tries to mount at 2TB1.
Thanks, I will do that. Currently reading the ArchWiki entry on udisks.
Much more stable and polished than KDE and I am running KDE myself. I think it only makes sense to run GNOME if you like the vanilla experience.
At this point I will probably just back up all the files and re-format the disk, as I can mount usb flash drives without any issue, so I am assuming there is something wrong with the external hard drive.