Error 0x8031002D

Value: -2144272339 | 0x8031002D | 2150694957

What does it mean ?

FVE_E_CANNOT_SET_FVEK_ENCRYPTED  
The drive encryption algorithm and key cannot be set on a previously encrypted drive. To encrypt this drive with BitLocker Drive Encryption, remove the previous encryption and then turn on BitLocker.
Value: 45 | 0x002D | 0b0000000000101101

Where does it come from ?

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

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