Hi andrenobre1988,
I have taken a carefully look at the link below:
https://technet.microsoft.com/en-GB/library/jj574173.aspx
For this prompt message:“Bootmgr failed to obtain the BitLocker volume master key from the network key protector".
There are multiple keys that could be generated and used by BitLocker
Some keys are required and some are optional protectors you could choose to use depending on the level of security you require.
I suggest you could use the Manage-bde.exe command-line tool to replace your authentication mode.
For more information about this command:
https://technet.microsoft.com/en-us/library/dd875513(v=ws.10).aspx
Additional resources:
https://technet.microsoft.com/en-sg/library/hh831507.aspx?f=255&MSPPError=-2147217396
Best regards,
Andy_Pan