It has been reported that users are unable to use the --encrypt option and or the --secure option via command line tools when using an embedded policy client.
When using the --encrypt command you will get the following error:
Operation start encrypt disk failed:
Error code -11984: Item not found
When using the --secure command you will get the following error:
Operation secure disk failed:
Error code -12220: Disk is already managed
This issue is fixed in the following release:
This version/Maintenance Pack is available for download via your account on Symantec File Connect.
You can still encrypt the drive via the user interface (GUI) of the Symantec Encryption Desktop application.