Error: Node Sass does not yet support your current environment: Windows 64-bit with Unsupported runtime (72)

Well, this is saying that python is not building CSS from Sass behind-the-scenes for you. Maybe beat the problem with this:

npm install gulp-sass

 
 

...or...

npm rebuild node-sass

 
 

...or even...

1. npm --add-python-to-path='true' --debug install --global windows-build-tools
2. npm config set msvs_version 2015
3. npm i node-sass@latest

 
 

You may need to press Ctrl-C to break between the first two steps above. I did.