I could be wrong, but having DirectX 12 support doesn’t mean that you are able to run SM6. I suggest checking the Windows version and the information below:
Requirement: *) OS: Windows 10 Creators Update 15063+. *) Windows SDK: Install Windows 10 SDK 15063+ to obtain DXC, the new shader compiler that supports SM6. Note that you might need to modify the paths in CompileShader_SM6.bat if you are using a SDK that is newer than 15063. For simplicity we point the dxc.exe path to 15063 SDK folder. *) Graphics Driver: See this page for details. Running Shaders · microsoft/DirectXShaderCompiler Wiki · GitHub