2X RDP Client for Windows x46 (12.0 (build 2212) - SSO feat8

When we install the 2X RDP Client for Windows x46 (12.0 (build 2212) on our 2008 R2 x64 RDS servers, the SSO option is available to install/enable via the General tab under options.

But trying the same install on a 2012 R2 RDS server the entire SSO option is missing the General tab under options. That being said the SSO checkbox is there when creating a connection, yet it is greyed out.

What options do we have to use the SSO option in the RDP client under 2012 R2 as an RDS session host? I have tried modifying the MSI and adding TUXGINASRV as a value of 1 to no avail.

2X RAS OS – 2008 R2 x64
2X RAS version – 12.0 build 2193

RDS OS – 2012 R2 x64
2X RDP Client version 12.0 build 2212

UAC off on 2012 R2 x64 RDS and 2008 R2 x64 RAS
No AV installed (testing) on 2012 R2 x64 RDS and 2008 R2 x64 RAS
Windows Firewall is off on 2012 R2 x64 RDS and 2008 R2 x64 RAS