This was about 2 hours of fuss that I wish I had avoided. With my updated Jupyter Notebooks, I need to be explicit about what conda environment for python I am using.
It is all laid out clearly, if only I had been looking in this bit of the IPython docs:
For example, using conda environments, install a
Python (myenv) Kernel in a first environment:
source activate myenv python -m ipykernel install --user --name myenv --display-name "Python (myenv)"
And in a second environment, after making sure ipykernel is installed in it:
source activate other-env python -m ipykernel install --user --name other-env --display-name "Python (other-env)"