No navigation bar on github pages

[jhconning]

I've used jupyterbook for many projects with github pages and github actions. But now, sites that build properly on my local machine are building without the navigation bar on github pages. Github actions tells me the book was built and deployed without error, yet no navigation bar. I can't figure it out. Does anyone have any suggestions as to what I might be doing wrong? Thanks!

A simple repo (JB builds this perfectly with navigation bar on a local computer) https://github.com/jhconning/jbook

The rendered github page with no navigation bar: (https://jhconning.github.io/jbook/