SQL 2016 MDS Web App error: SecurityException: Requested registry access is not allowed

Hope someone here can help...

Can't get SQL Server 2016 Master Data Services to work due to a registry permissions issue:

 SecurityException: Requested registry access is not allowed

I have no idea what registry key it's try to access.  The app pool is running under an AD account and the config tool added it to the MDS_ServiceAccounts group.  We had other issues with the install were I had to manually grant permissions to the web.config file, the MDSTempDir, etc. as described in the docs.  Unfortunately, there is no mention of the registry in the documentation that I could find.

Here's the version info:

Microsoft SQL Server 2016 (RTM-GDR) (KB3164398) - 13.0.1708.0 (X64)   Jun  2 2016 07:18:56   Copyright (c) Microsoft Corporation  Enterprise Edition: Core-based Licensing (64-bit) on Windows Server 2012 R2 Standard 6.3 <X64> (Build 9600: ) (Hypervisor)

Any ideas?

Thanks,
Jim