Error 0x803100D6

Value: -2144272170 | 0x803100D6 | 2150695126

What does it mean ?

FVE_E_VOLUME_EXTEND_PREVENTS_EOW_DECRYPT  
Device encryption can't be turned off while this drive is being encrypted. Please try again later.
Value: 214 | 0x00D6 | 0b0000000011010110

Where does it come from ?

FACILITY_FVE  
Full volume encryption
Value: 49 | 0x031 | 0b00110001

Other Errors for FACILITY_FVE