So, as a test to see if another kernel of python3 with a different name will work, could you follow the instructions here:
To setup another
python3 kernel with a different name, the
useful-project-name in the example, and see what happens when you try to run a notebook with that new kernel.
Because if that runs fine, there is something wrong with the particular
python 3 kernel that the notebook is trying to use. In which case you should remove it and replace with a fresh