Heikki,
I had the same issue with python3 on windows10.? For me it was an issue with being in the correct start directory when running quisk.? Ultimately i created a shortcut that solved the issue.
Here are my shortcut links with my username changed to <username> for security:
Target?C:\Users\<username>\AppData\Local\Programs\Python\Python38\python.exe quisk.py
Start in?C:\Users\<username>\AppData\Local\Programs\Python\Python38\Lib\site-packages\quisk?
The shortcut starts python3 with a command line of quisk.py while in the quisk package directory.
Let me know if this is your issue as well.
73
Evan
AC9TU