Error displaying widget: model not found -- how to fix this?

Widgets
3

This turned out to be the key:

jupyter labextension list

Note:

> jupyter labextension list
JupyterLab v3.2.4
.local/share/jupyter/labextensions
        @jupyter-widgets/jupyterlab-manager v4.0.0-beta.0 enabled OK (python, jupyterlab_widgets)

> pip uninstall jupyterlab_widgets
Found existing installation: jupyterlab-widgets 2.0.0b0
Uninstalling jupyterlab-widgets-2.0.0b0:

> pip install jupyterlab_widgets
Defaulting to user installation because normal site-packages is not writeable
Collecting jupyterlab_widgets
  Using cached jupyterlab_widgets-1.0.2-py3-none-any.whl (243 kB)
Installing collected packages: jupyterlab-widgets
Successfully installed jupyterlab-widgets-1.0.2

> jupyter labextension list
JupyterLab v3.2.4
.local/share/jupyter/labextensions
        @jupyter-widgets/jupyterlab-manager v3.0.1 enabled OK (python, jupyterlab_widgets)

Now it works again.

Thanks again.