Windows: Could not detect VapourSynth

Python 3.9.9 installed for all users with official installer
where python in cmd prints C:\Program Files\Python39\python.exe
python --version in cmd prints Python 3.9.9

Typing this in the python interpreter

from vapoursynth import core
print(core.version())

Yields this output:

VapourSynth Video Processing Library
Copyright (c) 2012-2021 Fredrik Mellbin
Core R57
API R4.0
API R3.6
Options: -

VapourSynth installed with installer, everything default
vsrepo available, vsrepo update etc in cmd all print Could not detect vapoursynth

I cannot figure out how meta_path works. Would greatly appreciate any help, thanks.

Update: I just found out executing the following code

import sys
for loader in sys.meta_path:
    if loader.find_module("vapoursynth") is not None:
        print("yes")
        break
else:
    print("no")

prints yes in the interpreter but prints no when saving it to a test.py and run it by test or test.py.

vapoursynth / vsrepo

Windows: Could not detect VapourSynth #172