Notebook files are not loaded.

[MiNeDevelop]

I have installed JupyterLab version 4.0.2. When loading the notebook files, I get the following error:Unreadable Notebook:

/Users/mine/Downloads/01_intro.ipynb <ValidationError: "Notebook could not be converted from version 1 to version 2 because it's missing a key: cells">

I tried to convert it with nbconvert:

jupyter nbconvert --to notebook 01_intro.ipynb --output test.ipynb

This provides the following output:

jsonschema.exceptions.ValidationError: Notebook could not be converted from version 1 to version 2 because it's missing a key: cells