Ugh sorry I'm on 0.98 of NSC Builder and getting that error.
Are you using the python version? If so you need to edit the zconfig file and change the pycommand line to whatever you use to call python.
If you're using the exe versions and downloaded my offline file i inclded the python confi files the other day by mistake. I fixed it shortly after but is poible someone downloaded the config file.
The lines in the file that change are:
(zconfig\NSCB_options.cmd)
python:
set "pycommand=py -3"
set "nut=ztools\squirrel.py"
set "zip=ztools\squirrel.py"
set "listmanager=ztools\squirrel.py"
x64 or x86
set "pycommand="
set "nut=ztools\squirrel.exe"
set "zip=ztools\squirrel.exe"
set "listmanager=ztools\squirrel.exe"
If you use other command to call python then pycommand needs to be that command. Examples:
python command
set "pycommand=python"
conda command (Anaconda distribution)
set "pycommand=conda"
You can edit the file with an text editor like notepad++