Grateful for any recommendations. Need to recover the data.
The drive was occasionally unmounting for no known reason, but that seemed to clear up when I moved it off the powered USB hub and onto the un-used USB port on the Mac. Now unable to mount. First aid fails with fsck returning error 8.
$ diskutil info disk3s2
Device Identifier: disk3s2
Device Node: /dev/disk3s2
Whole: No
Part of Whole: disk3
Volume Name: MacBackup
Mounted: No
Partition Type: Apple_HFS
File System Personality: Journaled HFS+
Type (Bundle): hfs
Name (User Visible): Mac OS Extended (Journaled)
Journal: Unknown (not mounted)
Owners: Disabled
OS Can Be Installed: No
Media Type: Generic
Protocol: USB
SMART Status: Not Supported
Volume UUID: 5F96501D-C3BF-3AAE-96E9-FB78678E44D5
Disk / Partition UUID: 6B9F85C6-7A39-4F2A-A91D-DD9ADC344AA7
Partition Offset: 209735680 Bytes (409640 512-Byte-Device-Blocks)
Disk Size: 2.0 TB (2000021315584 Bytes) (exactly 3906291632 512-Byte-Units)
Device Block Size: 512 Bytes
Volume Total Space: 0 B (0 Bytes) (exactly 0 512-Byte-Units)
Volume Free Space: 0 B (0 Bytes) (exactly 0 512-Byte-Units)
Read-Only Media: No
Read-Only Volume: Not applicable (not mounted)
Device Location: External
Removable Media: Fixed
Virtual: No