Error 0x8031002E

Value: -2144272338 | 0x8031002E | 2150694958

What does it mean ?

FVE_E_CANNOT_ENCRYPT_NO_KEY  
BitLocker Drive Encryption cannot encrypt the specified drive because an encryption key is not available. Add a key protector to encrypt this drive.
Value: 46 | 0x002E | 0b0000000000101110

Where does it come from ?

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

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