This may be because you're using a different node-sass version than the one I use in the videos. Please uninstall node-sass with:
npm uninstall node-sass --save-dev
Then install version 4.5.3 with;
npm install node-sass@4.5.3 --save-dev.
This is more of a workaround if Solution 1 doesn't work. You can install a package called nodemon to run node.js code directly. Install it with:
npm install nodemon --save-dev
Then in the package.json file, add the following tasks:
"compile:sass": "node-sass sass/main.scss css/style.comp.css"
"watch:sass": "nodemon -e scss -x \"npm run compile:sass\""
If you're using VSCode, the defualt autosave setting is that it saves your file each time you stroke a key. This made me run into some errors in the videos. The fix is to change the autosave setting to onFocusChange. You can do so by copying the following instruction to the settings (panel on the right side):
"files.autoSave": "onFocusChange"
On Windows you will have to escape the " in the autoprefixer task, just like this:
"prefix:css": "postcss --use autoprefixer -b \"last 10 versions\" css/style.concat.css -o css/style.prefix.css"
If your NPM packages don't work at all, please make sure you have at least node v6.x.x installed on your computer. You can check your version with node -v.
You can also try setting all your NPM packages to the same versions used in the videos. It works like described in Q1 of this document (node-sass example). These are the versions I used in the videos:
"autoprefixer": "^7.1.4",
"concat": "^1.0.3",
"node-sass": "^4.5.3",
"npm-run-all": "^4.1.1",
"postcss-cli": "^4.1.1"
I will keep this document updated if more issues arise.