BitLocker automatic device encryption is enabled only after users sign in with a Microsoft Account or an Azure Active Directory account. BitLocker automatic device encryption is not enabled with local accounts, in which case BitLocker can be manually enabled using the BitLocker Control Panel.
Dell computer is special, I see many user meet with this situation: BitLocker needs a key but user never installed it.
Note for DELL devices: If you own a Dell PC or laptop and you have added a Microsoft account (MSA) on you device, for any reason (e.g. if you use an MSA account to logon to Windows 10, or to download Apps from the Microsoft Store, or to get your emails, or to activate Microsoft Office), then from another device with Internet access, sign in with that Microsoft Account at Microsoft's Bitlocker Recover Key webpage to get the Recovery key for your device. **
Source:
https://www.wintips.org/fix-dell-laptop-needs-the-bitlocker-recovery-key/
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