Unexpected ConfigurationType" error when attempting to onboard to Defender ATP with MECM

Crossposting from the Security and Compliance forum...

I'm attempting to onboard some clients to Defender ATP using Microsoft Endpoint Configuration Manager. I've followed the instructions here: https://docs.microsoft.com/en-us/windows/security/threat-protection/microsoft-defender-atp/configure-endpoints-sccm

However, the clients are not being onboarded, and when I look at the C:\Windows\CCM\Logs\ATPHandler.log file, I see the following:

ATPHandler: Handling policy originating from AdminConsole: AdvancedThreatProtectionSettings_Configuration	2020-10-21 5:09:35 PM	10148 (0x27A4)
ATPHandler: Unexpected ConfigurationType, 	2020-10-21 5:09:35 PM	10148 (0x27A4)
ATPHandler: Failure in CATPHandler::HandleUIPolicy: 0x80070057	2020-10-21 5:09:35 PM	10148 (0x27A4)

I haven't found any reference to this "ATPHandler: Unexpected ConfigurationType" error anywhere. Does anyone know what I should be looking at to troubleshoot this?

MECM Client version 5.00.9012.1034, site version 5.0.9012.1000