I tried recompiling my bachelor thesis in latex today and encountered problems with the pdfpages package. While it worked perfectly when I originally compiled the thesis it now throws "undefined control sequence" errors. The new pdfpages package is "packaged on 24/09/2019". Miktex console version is 2.9.7206
I tried compiling it with an old version I still had on my desktop pc which worked without a problem. After updating the miktex packages it stopped working there as well. I also produced a minimal file which does nothing but trying to include a pdf file and this also produces the error. So it's not any other package or code I used in the thesis.
\documentclass{scrartcl}
\usepackage{pdfpages}
\begin{document}
\includepdf[pages=-]{test.pdf} %Use any pdf you want to try.
\end{document}
While on the old version it would work as expected including the pdf document in the output the updated package just throws the error "undefined control sequence" 6 times and a single "file filename.pdf not found" error.
Thanks to Samcarter. Seems to be a temporary miktex problem with the graphicx package which is used in the background of \includepdf. Thanks to all the other answers as well.
@Edit: True to Samcarters words the problem was not fixed for me. After updating all the packages I had to rebuild the formats (miktex console -> settings -> formats -> rebuild (I rebuild latex, pdflatex, pdftex from user mode) After that it worked fine again.