appreciate the kind help. Unfortunately these doesn't help.
My problem aren't really nmake. I'm using 2020 R2, I have the feature to enable "Built-In Compilers"

So the problem Statement is, when in Compiled UDFs
Built will result following Error
"'C:\PROGRA~1\ANSYS' is not recognized as an internal or external command, operable program or batch file."
LOAD will result following Error
"Error: The UDF library you are trying to load (libudf) is not compiled for parallel use on the current platform (win64).\n\nThe system cannot find the file specified."

Do ANSYS staff knows, with Build-In Compiler, is the problem still lies within Visual Studio? Because if it doesn't we can certainly skip the MS Visual Studio and look other way.
Or the problem is more to the Build-in Compilers itself. Is there anyway to check on Build-In Compilers? DO we have any patch and installer to re-install on ANSYS Patch?