Lots of possibilities for failing at the enable bitlocker task. Things to check:
TPM is enabled
If re-imaging make sure TPM has been cleared in the BIOS
SCCM service account has proper permissions to the OU
A new one for me was trouble with Panasonic CF33 2-in-1 devices. Even though they have a connected keyboard Microsoft still categorizes these as "slate" devices like the MS Surface or other 2-in-1s.
In the SMSTS.log I found the following error:
"Failed to run the action: Enable BitLocker.
No pre-boot keyboard or Windows Recovery Environment detected. The user may not be able to provide required input to unlock the volume. (Error: 803100B6; Source: Windows)"
To optimize hard drive space I delete the recovery partition when partition the disk which is one reason for this error. Another fix is to add a reg key that tells Windows to ignore the no pre-book keyboard warning:
reg key HKLM:\SOFTWARE\Policies\Microsoft\FVE\OSEnablePrebootInputProtectorsOnSlates=1
You can create a CMD task right before Enable Bitlocker with the following command and that will fix this issue:
powershell.exe -command "New-Item -Path HKLM:\SOFTWARE\Policies\Microsoft -Name FVE; Set-ItemProperty -Path HKLM:\SOFTWARE\Policies\Microsoft\FVE -Name OSEnablePrebootInputProtectorsOnSlates -Value 1 -Type DWord -Force"