nbinteract failed with matplotlib

[OrFixelAlgorithms]

Hi, I used this requirements file: https://github.com/FixelAlgorithmsTeam/FixelCourses/blob/master/requirements.txt

and this ipynb: https://github.com/FixelAlgorithmsTeam/FixelCourses/blob/master/Test1.ipynb

when I convert to HTML and open the file I get the following error:

Any suggestions?