NBD Server mounts drive, but not detecting it

[TheMrIron2]

I followed the instructions in "How to Setup NBD Server (Network)" in the README.
When I reached the last step, I heard the Windows sound effect that indicates a new drive has connected... but it does not appear as a local drive, and PFS Manager does not detect the drive.

It does appear in "Show list of mounted devices":

And in Windows Device Manager, as an "Unallocated" drive:

However, it does not show up in File Explorer, and PFS Manager still says "[NO DEVICE] PLEASE RELOAD HDD". Trying to rescan HDDs at the main menu reports "Playstation 2 HDD Not Detected / Drive Must Be Formatted First".

TL;DR I followed the instructions and connected via NBD, but PFS is not detecting the PS2 HDD.