Google PageSpeed Insights is a tool for web developers to help them achieve maximum performance. It provides insights on how to optimize a web page and how to make it faster.

There are different ways to get the score of a web page. For instance, you can get it from your browser, from a website, or from the PageSpeed Insights extension. This extension allows you to go deeper in looking into your website's stats. It is very simple and easy to use. 

If the extension is not working, try updating it and reinstalling it on your browser.