How did you configure it? Are you seeing any errors in your browser console?
Someone configured Hotjar succesfully before: Run a Hotjar script
Also check this topic for more clues: How to add "feedback" floating button like this site - #4 by AnkitJain
And this guide may be helpful, since HubSpot seems to have a similar survey feature (check note at the end of the topic) HubSpot chat integration