Why can't I import the package that I just installed?

I recently started learning flutter/dart and I have a Problem that i couldn't solve. I've read in the official flutter documentation that you have to follow these three steps to install a package in flutter:

1. Add the package (in my case: 'english_words: ^3.1.5') to the dependencies in the pubspec.yaml file.
2. Run the 'flutter pub get' command to include the package to the '.packages' file.
3. Add import 'yourpackagename' (in my case: 'package:english_words/english_words.dart') to the main.dart file.

My problem is though that VS marks it as an error if I try to do step 3: Target of the URI doesn't exist

Any ideas what I could do? I've installed the flutter and dart extensions for VS Code and also tried to restart the program but nothing worked.

try running

flutter clean

if it is still not working, run:

flutter clean pub cache