Server: R730xd
Controller: H730P
Drives: 2x Samsung PM1643 (RAID 1)

In iDRAC when I choose Storage > Virtual Disks > Manage > Virtual Disk Actions > Encrypt Virtual Disk and click Apply the tasks complete successfully in the job queue but in the list of virtual disks the "Secured" property stays at "No" and two errors are logged to the Storage Events log (see below). The drives are TCG-compliant SED and the controller has been setup with a security key. Is there something that I'm missing or is the SED feature of these drives incompatible with the controller?

Security subsystem errors detected for Disk 12 in Backplane 1 of Integrated RAID Controller 1
Security subsystem errors detected for Disk 13 in Backplane 1 of Integrated RAID Controller 1