I cloned your repo locally and used TeXStudio to compile your repo as is - I did get the diagram to print into the pdf but it printed on a new separate page and the right side of it was cut off (the diagram that printed was much larger than the width of the page).
I noticed in your code that you commented out:
%\includegraphics[width=0.7\textwidth]{./mg-hierarchy.png}
And are instead using:
\includegraphics{mg-hierarchy}
In order to get the image to print correctly I changed that line to:
\includegraphics[width=1.0\textwidth]{mg-hierarchy}
This sets the image to print to the width of the text. Please try this to fix the issue as it worked locally for me.
I cloned your repo locally and used TeXStudio to compile your repo as is - I did get the diagram to print into the pdf but it printed on a new separate page and the right side of it was cut off (the diagram that printed was much larger than the width of the page).
I noticed in your code that you commented out: %\includegraphics[width=0.7\textwidth]{./mg-hierarchy.png}
And are instead using: \includegraphics{mg-hierarchy}
In order to get the image to print correctly I changed that line to: \includegraphics[width=1.0\textwidth]{mg-hierarchy}
This sets the image to print to the width of the text. Please try this to fix the issue as it worked locally for me.