Windows 10: How to recover the bitlocker key to a device that is out of service and unlinked?

One of my computers died and I sent its hard drive to a recovery service to recover the files. The engineer asks for the hard drive's Bitlocker key. Problem is I unlinked that computer from my account after it's down so it's not on the device list anymore. It is not working now so I cannot relink it. How can I recover its Bitlocker key and other information that is necessary to recover my hard drive?

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Recover BitLocker key from Key ID

It doesn't work. The specific device I need to recover the key is not on the list, neither an option to retrieve the BitLocker code using its Key ID as the blue screen says.

 

BitLocker Recover

My MS account has my device listed and a link to access my BitLocker recover key but it doesn't work, how do I get this? HELP!

 

BitLocker Key

There may be a software that triggered the BitLocker in your Windows 10 PC. To assist you better, we suggest that you check these articles for further information:

• Find my BitLocker recovery key.
• BitLocker recovery keys: Frequently asked questions.

• BitLocker

Let us know if you need further assistance.