@Carol Tsang
Hi,
What update were you doing? You need to disable BitLocker to permit firmware updates, it is suggested to suspend BitLocker when you updating BIOS.
If you don’t do that, it may trigger BitLocker recovery mode.
The following information may help you locate your recovery key:
https://support.microsoft.com/en-us/windows/finding-your-bitlocker-recovery-key-in-windows-10-6b71ad27-0b89-ea08-f143-056f5ab347d6
If the recovery key is lost, the drive cannot be unlocked by other means.
Your only option may be to reinstall your PC.
Hope above information can help you.
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