Impossible to unlock WD My Book Duo 6 To

I just bought a 6 TB (2 x 3 TB) WD My Book Duo and I installed the WD Security, WD Drive utilities software. Everything works fine because the disk is recognized and I can write to the disk. I then wanted to protect the access to the disk with a password and I used WD Security to set a password. When I stop the WD My Book DUo, I unplug it from my PC, and plug it back in, the access to the disk is locked before password but when I write the password I just chose, WD Security displays the following error message: invalid password.
I tried to erase everything on the disk with WD Drive Utilities, reformat the disk and redefine a new password to pass, I still have the same error message and unable to access to my disk WD My Book Duo.
Thanks a lot for your help.