Please disable fast boot in the BIOS and ensure that BIOS revision M71 ver 01.09 or later is installed. - KB86399
Also, the 820 G2 requires the Hardware Compatibility XML. Likley this is already updated being you are running 184.108.40.2064 but won't hurt updating anyway. As a good practice, before attempting to encrypt any new systems it is a good practice to download the current version of the HwCompXML attached to the bottom of KB81900.