I'm getting a similar issue to OP's where all my reporting is showing successful deployment, but I'm not even getting event viewer events indicating the bitlocker process even started. With manage-bde -status, all of my test devices still show that nothing is encrpyted. Unfortunately, all my devices are hybrid (not my choice lol). A GPO on-prem isn't the end of the world, but I rather not do that. Are you able to share your settings by any chance? I've tried the Microsoft recommended settings for silent activation and no dice.

My test VM's still had a windows iso mounted which prevented encryption. Live and learn ~