I was having issues with getting CrashPlan to backup to network storage (a Western Digital MyBookLive). In short, the drive was not always mapped. I fixed it using advice given in this article:
https://support.code42.com/CrashPlan/4/Backup/Back_up_files_from_a_Windows_network_drive
The batch file looked like this:
net use Z: /DELETE net use Z: "\\192.168.0.13\Andy" "password here" /USER:"username here" >>E:\mount_drive_for_crashplan.log
And I created a scheduled task to run it as instructed in the article.