Problem rendering figures with Documenter.jl

I’m having problems rendering figures (from Plots.jl) in the generated notebook documents. I do convert the Jupyter notebooks to MD and passed to the makedocs. It used to work but now the browser (Safary & Chrome) renders the source of the figure and not the figure.

<?xml version="1.0" encoding="utf-8"?> <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="1000" height="800" viewBox="0 0 4000 3200"> <defs> <clipPath id="clip820"> <rect x="0" y="0" width="4000" height="3200"/> </clipPath> </defs> <path clip-
...

See for example

The way I generate the MD file is with run(`jupyter nbconvert --execute --to=markdown --output-dir=$output_dir $notebook`) and the passed to makedcs.

See the full code.