I have very often the issue with F11 in Visual Studio Code when working with Python. Imagine you want to step into the function (F11) and it just doesn't want.
To workaround this you should add the property debugStdLib in the launch.json file as shown at the picture below.
The position of the attribute marked with red arrow is wrong. You should use the attribute at the place marked with the green arrow. Yes, VS strike it out as it would be incorrect. But the VS does not mean that seriously. Just put it in there and all will work fine.