Hi Takeshi,
Have you checked out this community post? Your Answers experience needs to be set up to listen to events from other parts of the page. If you built your Answers experience using the Help Site or Support Solution template then that is already in the experience.
Also, to confirm, did you install the app from the Salesforce App Exchange and follow steps 5 and 6 from this guide to add case deflection to your Salesforce help site?
Let me know if that helps!
Thanks!
Dana