After a system has been encrypted with Symantec Encryption software, a preboot screen will be displayed to authenticate and boot a machine. On Lenovo P52 systems, the keystrokes are not registered properly and may not allow proper authentication.
This is due to the system being imaged with Legacy BIOS.
This issue no longer occurs once the machine has been imaged with UEFI. UEFI is the recommended method to resolve this issue as it is the go-forward BIOS new machines are shipping with and is more secure.
As a workaround to this issue, plug in an external keyboard to authenticate properly at preboot.