If you don't know your BitLocker key, you may look for your BitLocker recovery key in your Microsoft account: Sign in on another computer or phone to see BitLocker recovery keys.
The following information may help you locate your recovery key:
If the recovery key is lost, the drive cannot be unlocked by other means.
Meanwhile, if the laptop now runs fine, search on your computer for BitLocker. You may be taken to "Control Panel\All Control Panel Items\BitLocker Drive Encryption" and chose the "Backup recovery key" option.
You can save it to the cloud, to file or print it out.
Also, the following conditions have to be met for Windows to automatically enable the BitLocker:
InstantOn (Modern Standby)
Logged in with Microsoft or Azure AD account (not a local account)
Under these conditions Windows may automatically encrypt the drive and upload a copy of the recovery key to their Microsoft/Azure account.
Hope above information can help you.
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