Cannot mount exFAT exterior drive in macOS

I’ve a Western Digital MyBook (25EE) 8TB Exterior Drive. It’s formatted with exFAT. I am unable to recall precisely the way it was formatted, however I imagine it was finished with Synology’s DiskStation for my Synology NAS. I’m able to mount and browse the drive after I join it to the NAS, however not on macOS Sierra 10.12.6.

The drive exhibits up in Disk Utility, however mounting does nothing. I’ve run “First Support” with no errors.

Disk Utility incorrectly thinks that the utilization is 8/8 TB. As could be seen within the screenshot under, utilization is round 4.2/8 TB. The drive primarily incorporates a Synology HyperBackup file (.hbk) which makes up nearly single-handedly all of these 4.2 TB.

In response to Synology DiskStation, the primary partition is exFAT and I believe the EFI partition is vfat:

The drive additionally exhibits up in diskutil as disk2s2 however I am unable to mount it:

/dev/disk2 (exterior, bodily):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *8.0 TB     disk2
   1:                        EFI EFI                     209.7 MB   disk2s1
   2:       Microsoft Primary Information WD My Guide              8.0 TB     disk2s2

$ mount disk2s2
mount: disk2s2: unknown particular file or file system.

$ diskutil mountDisk disk2
A number of quantity(s) did not mount

NB: (I attempted following these directions for FUSE for macOS, however I suppose they’re probably not related since exFAT must be supported natively in macOS lately.)

I haven’t got the faintest thought the place to start out on this subject – what could possibly be the issue right here?

---

Edit 1: Block Sizes

macOS:

$ diskutil data disk2 | grep "Block Dimension"
   Gadget Block Dimension:        512 Bytes

$ diskutil data disk2s1 | grep "Block Dimension"
   Gadget Block Dimension:        512 Bytes

$ diskutil data disk2s2 | grep "Block Dimension"
   Gadget Block Dimension:        512 Bytes

Synology SSH:

Used fdisk -l. Discover the GPT PMBR measurement mismatch – perhaps it has some relevance?

GPT PMBR measurement mismatch (4294967294 != 2743150591) might be corrected by w(ceremony).
Disk /dev/sdq: 7.3 TiB, 8001562869760 bytes, 15628052480 sectors
Items: sectors of 1 * 512 = 512 bytes
Sector measurement (logical/bodily): 512 bytes / 4096 bytes
I/O measurement (minimal/optimum): 4096 bytes / 4096 bytes
Disklabel sort: gpt

Gadget      Begin         Finish     Sectors  Dimension Sort
/dev/sdq1      40      409639      409600  200M EFI System
/dev/sdq2  411648 15628050431 15627638784  7.3T Microsoft primary information

---

Edit 2: GPT

$ sudo gpt -r present disk2

        begin         measurement  index  contents
            0            1         PMBR
            1            1         Pri GPT header
            2           32         Pri GPT desk
           34            6         
           40       409600      1  GPT half - C12A7328-F81F-11D2-BA4B-00A0C93E####
       409640         2008         
       411648  15627638784      2  GPT half - EBD0A0A2-B9E5-4433-87C0-68B6B726####
  15628050432         2015         
  15628052447           32         Sec GPT desk
  15628052479            1         Sec GPT header

---

Edit 3: Mounting EFI

Apparently macOS is ready to mount and Finder checklist the contents of the EFI.

$ diskutil mountDisk disk2
A number of quantity(s) did not mount

The amount that fails to mount is the first exFAT quantity. macOS requires the EFI quantity to be unmounted or it is going to complain about not correctly ejecting disks.