is it possible to run the nnn File Manager on Windows?
Using PowerShell I successfully installed nnn (https://github.com/jarun/nnn) [with]
PS> python.exe -m pip install nnn
Are you certain you installed the project you wish to use? Because nnn from PyPI (where -m pip install nnn would normally get files from) looks to be a completely different application.
Superficially, it seems to be some sort of number reversing utility with no clear links to the GitHub project you linked in your original question. Furthermore, the "nnn" project on GitHub doesn't even appear to based primarily on Python.