Server 2012R2 Authorization Policy Error when Adding new policy either RD CAP or RD RAP
I started a Microsoft support call about this already. I managed to figure out that the issue is caused by KB3102467 which is the .NET Framework 4.6.1 for Windows Server 2012 R2 on Windows Update. Apparently The remote desktop gateway manager mmc is not fully supportive of .NET 4.6.1 I remove the update and remote desktop gateway manager let me add policies again after I restarted the server.
https://support.microsoft.com/en-us/kb/3102467
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