If nothing is happening when you click the link then you most likely have a javascript error in your Dashboard stemming from another plugin or your theme. The Post Duplicator uses javascript and ajax to duplicate the post and then reload the page. If your site has a javascript error, then this script will not run, thus, nothing will happen.
The plugin does work, I assure you https://www.ads-software.com/support/plugin/post-duplicator/reviews/?filter=5.
You should be able to track down where a potential error is coming from by following through this article https://www.metaphorcreations.com/article/test-plugin-conflicts/
