Exceeding 2Tb limit questions

WD External Drives External Drives for PC
9

I’m almost certain your drive is partitioned in MBR mode, not GPT. The way that the My Book circumvents the 2TiB MBR limit is to use 4KB LBAs rather than 512 bytes.

You could easily confirm this by examining sector 0 with a disc editor. It would be most helpful if you could upload its contents.

DMDE (DM Disk Editor and Data Recovery Software):
http://softdm.com/download.html