When browsing a client from the BACKUP window the below pop up error is returned:
"No plugin available"
Checking the client properties from the NVBU server's Client management shows all plugins are installed.
All other clients display and backup fine.
The ../netvault/pits directory may be missing, or missing a file, or its file(s) may be corrupt.
There should be a ../netvault/pit.pre or pit.old directory with needed files (should have 3 files, IconsAndMethods, InstalledPlugins, and version) . Try renaming the pits directory to something else, and rename pits.pre to pits, which should resolve the issue.
Alternatively, if there is a client working fine with the same OS and NVBU version, copy its pit folder over to the problem client and try again.