By default, the mounted Vaults are only visible for the current user.
This also means Windows services (without logon) cannot see the decrypted vault contents. This means some backup tools, Windows sharing, 'Run .exe as Administrator', .. do not work.
Since version 9.8.4.2 you can set this option in the Dashboard Settings so that those services and all logged on users can see your mounted vaults.
Go to Tools -> Options
Select Mount for all users
Restart the client