@Dilan Nanayakkara , From your description, I know the silently enable Bitlocker with Autopilot is failed. If there's any misunderstanding, please let us know.
Based as I know, to enable Bitlocker silently during Autopilot, we need to make sure the ESP is enabled. When it is enabled, then the Device Encryption feature will wait until Intune policy assignment happens, and then BitLocker can be turned on and applicable settings can be used. We can follow the steps in the following link to configure to see if it is working:
https://learn.microsoft.com/en-us/mem/autopilot/bitlocker
Hope it can help.
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