Ran into a rather peculiar problem after upgrading to version 4.20. The intelisense is indicating that none of my header files can be read and when I try to compile the project, I get the error message Unable to expand variable in ‘$(DXSDK_DIR)\Lib\x64’ TheMissingFew M:\Documents\Project\Intermediate\ProjectFiles\UnrealBuildTool 1. Anyone know why this could be?
Check this thread. They seem to have the same problem 
My bad, did not see this- thanks