Failed to download - This generally signifies a permissions error, The scan does not have the correct credentials to access the file, or additional access controls exist on the file, or AD access may have been interrupted (try to manually access the files using the DLP scan user to see why the download failed)
Access is denied - This error is generally caused by permissions in the environment related to the dlp scan user and the share (try to manually access the files using the DLP scan user to see why the download failed)
The specified path cannot be found -- System error 53 has occurred. The network path was not found - This error is related to network configuration or firewall blocking communication to from the Discover server to the target file server
No such mount exists -- x - this can be related to file reader restarts, when the file reader does not unmount the drive fully during the restart and then the scan cannot mount the drive to continue scanning.