Yet another root folder not found issue

Sonarr version: 2.0.0.5344:
Windows 10 64 bit version 1909 os build 18363.836:
Debug logs see below:
Description of issue:

Sonarr as a service has been working trouble free for a couple of years, then decided the unc root directory no longer exists. Have tried all kinds of troubleshooting - running as a console as administrator, changing service logon parameters from local account and rebooting, to back to an adminstrator login, etc etc. the unc root directory is always present and accessible on the computer. Also, Radarr has been running fine the whole time. Need more ideas, please?

[Error] FreeSpaceSpecification: Unable to check free disk space while importing.

[v2.0.0.5344] System.IO.DirectoryNotFoundException: \wdmycloud\public
at NzbDrone.Windows.Disk.DiskProvider.GetAvailableSpace(String path) in C:\BuildAgent\work\5d7581516c0ee5b3\src\NzbDrone.Windows\Disk\DiskProvider.cs:line 33
at NzbDrone.Core.MediaFiles.EpisodeImport.Specifications.FreeSpaceSpecification.IsSatisfiedBy(LocalEpisode localEpisode, DownloadClientItem downloadClientItem) in C:\BuildAgent\work\5d7581516c0ee5b3\src\NzbDrone.Core\MediaFiles\EpisodeImport\Specifications\FreeSpaceSpecification.cs:line 42