Own module import started failing

It was working fine yesterday, but today I have been getting this error when importing one of my own modules,

ModuleNotFoundError: No module named ‘pct.putils’

where pct is my lib_name and putils is a package from 01_putils.ipynb.

My notebooks are in nbs, as set in settings.ini.

I have installed in venv with pip install -e .

And have the following in the notebook I am importing from,

# hide
import sys

I have reverted all the changes I made today, but still have the problem.

Any idea what is going on, and how to resolve?