Reference: https://docs.microsoft.com/en-us/windows/device-security/tpm/backup-tpm-recovery-information-to-ad-ds
So you need MBAM instead. Which is in general a good idea.
But for MBAM in general you need MDOP under SA. And there is a constellation where you cant get MBAM normally when buying Windows under CSP.
There is as always a solution. Recovery key out of the Azure AD Box :-)

Pieter Wiegleven had here documented the full solution:
https://blogs.technet.microsoft.com/home_is_where_i_lay_my_head/2017/06/07/hardware-independent-automatic-bitlocker-encryption-using-aadmdm/
Have fun!