Home directory is not defined

[paulgeisler72]

When I run pdflatex on windows 10 (MiKTeX v21.2), I'm getting error "pdflatex: Home directory is not defined" and "Sorry, but pdflatex did not succeed." Running pdflatex on my personal work PC running windows 10 works fine. But I'm getting this error when I run pdflatex on our build server that runs windows 10.

[paulgeisler72]

It turns out the problem was that one or more of these environment variables was not defined.
%USERPROFILE%
%HOMEDRIVE%
%HOMEPATH%