It probably has to do with the Mathjax path specified in Doxyfile.in. The path starts with http whereas it should start with https.
MATHJAX_RELPATH = http://cdn.mathjax.org/mathjax/latest
Additionaly, cdn.mathjax.org should not be used, because this CDN has shutdown and the path is just a redirection of cdnjs.cloudflare.com, see https://www.mathjax.org/cdn-shutting-down/
The math (latex formulas with Mathjax) does not render when the manual is loaded in https, but it does render when the manual is loaded in http.
Example : https://umontreal-simul.github.io/latnetbuilder/d6/d4c/feats_figures.html http://umontreal-simul.github.io/latnetbuilder/d6/d4c/feats_figures.html
It probably has to do with the Mathjax path specified in Doxyfile.in. The path starts with http whereas it should start with https. MATHJAX_RELPATH = http://cdn.mathjax.org/mathjax/latest
Additionaly, cdn.mathjax.org should not be used, because this CDN has shutdown and the path is just a redirection of cdnjs.cloudflare.com, see https://www.mathjax.org/cdn-shutting-down/