My 2TB external HD was recognised by Disk Utility (but not finder), and Verify Disk was showing no problems. But, it still was unmounted NTFS-3G. So I tried 3rd party software to help my mac read the NTFS-3G file system. I've installed Mounty, Fuse with NTFS-3G, and Tuxera NTFS for Mac, all at the same time, then restarted my mac. Now, my Seagte NTFS-3G is recognized by finder. One of those programs worked. I am able to backup my files to a diffferent HD. I hope this helps. Good luck.