I can confirm that it is working fine on my web site. First, visit your Debounce console and do an email test there: https://app.debounce.io/single-validation
Second, be sure that you did not set a wrong CORS value in the Debounce API settings.
Once you get the test function working in WordPress, then in Gravity Forms it will validate the email once you press the form submit button. Feel free to visit my site and try it on our main contact form. https://www.ufcinc.com not hyperlinked in this post.
I an help you if you want. Ping me. jimhill10 at g mail dot com