I fixed this by completely uninstalling Stablebit DrivePool and Stablebit Scanner. After reboot, I reinstalled both apps. DrivePool automatically detected the pools in the disks and re-listed them.
However, this did not fix the issue right away.
The major improvement was that I was able to unassign the drive letter in DrivePool. Then I immediately re-selected "Assign drive letter" and Windows gave me back the same letter.
Again, at this point, the problem was sill not fixed, but I was able to give the drive letter a label. Using file Explorer, right clicked on "K:\Local Disk - Unlabled Volume 8, I selected rename and named it "DrivePool".
This was a critical turning point, with the label, I was able to share the drive again.
There is still an issue, DrivePool is not seeing the label and isnt detecting file system type:
If I switch to my other pool, it is working as expected:
@STAFF
If there a known issue if I use the label "DrivePool"? Should I use a different name?