Sometimes Blancco Drive Eraser / Blancco 5 might not be detect connected SATA drives (one or more). Usually this happens because the hard drives have been set to IDE/ATA mode in BIOS.
SATA drives need to be set in either "AHCI" or "SATA native" mode (or similar) from BIOS/UEFI/EFI.
IDE mode for SATA drives is not supported by Blancco Drive Eraser / Blancco 5.