After the SeqSphere+ server was installed as Windows Service (which is the default) it cannot access network drives that require user authentication. To access network drives (e.g., for backups) you need to change the account under which a service runs.

For a step by step description for this, see: https://technet.microsoft.com/en-us/library/cc755249.aspx

The service name of SeqSphere+ is 'Ridom SeqSphere Server'.