Nothing has happened
Firstly, have you installed and activated the plugin? See the installation instructions for details.
Secondly, if the plugin is being reported as active, are all of your topics fresher than the configured threshold? If so, dont worry, they all passed the test.
I have no topics!
Deactivate the plugin - everything will return. Now check the freshness of the posts in your topics. Its possible that none are passing the "freshness" check.
How do I configure the freshness threshold
Take a look in the freshness directory, at freshness.php - at the top of the file is a constant you can modify. The plugin works in terms of days - by default filtering anything older than 90 days. Feel free to change that value.