The webwork hardcopy generator shows the error only at \webworkSetCopyrightFooter, but when I download the TeX source and make webwork2.sty available than the \fancyfoot in the definition of \webworkSetCopyrightFooter seems to show up as undefined when using the distribution provided texlive 2019.
Installing manually texlive 2023 and changing to it in site.conf did resolve the problem, but installation took much longer than using the package manager.
Attached is the source file.