Recently I was installing MBAM 2.5 SP1 client on Windows 10 1903 during a ConfigMgr task sequence. Once the device was built and the user tried to put in a pin and start the encryption it would fail.
The below error was showing in the MBAM event logs. We currently install MBAM successfully on Windows 1809 so it didn’t look like a MBAM server issue or connection issue. I checked and there was a newer servicing release from May 2019
This update adds support for Windows 10 1903. I applied this update and can now encrypt successfully. Hopefully this helps if anyone else runs in to the same error.