Failed to load model class 'WebguiModel'

Dear developers,
My name is Mauro Sgroi and I am trying to use NGSolve to teach FEM to my students at the University of Torino.
I installed a full conda environment (last version, python 3.12) and then installed netgen/ngsolve using pip as described on the website.
The webgui_jupyter_widgets are installed too.
When executing the tutorial notebook on Poisson’s equation, I get the following error when plotting (Draw(gfu)).

I have no idea how to solve the problem because I am not an expert in using Jupyter notebook.

I would appreciate your help!
Thanks a lot in advance and best regards,
Mauro Sgroi.

Dear all,
solved downgrading to Python 3.11.