Are these notebooks up to date?
For example, this one seems to suggest that the 9n can be solved in a few minutes:
https://github.com/IIT-EnergySystemModels/openTEPES-tutorial/blob/8b47410ba66479a94308c6096913cbc2cc728caa/notebooks/01-openTEPES-Demo.ipynb
But when I run openTEPES with the 9n case, it takes more than an hour to solve.
e.g.:

You can see it says 3437 seconds (~57 minutes).