This post explains why BitLocker might be missing or not showing in Control Panel on your Windows 11/10 and the steps you can take to resolve the issue.

What Is the “Cannot Install Windows, BitLocker Drive Encryption Is Enabled on Selected Partition” Error? Windows 11 and old versions of the Windows operating system have BitLocker Encryption ...

The Windows 10 boot and shared data partitions somehow got encrypted with Bitlocker (and thus are inaccessible from the Win 8.1 install) after a repair shop swapped the motherboard.