Webhooks will not trigger automatically or manually

New to Prismic -- I created a webhook with the configuration shown below but it simply will not fire. I've tried publishing documents directly and through releases, and even clicking the "trigger it" button for the webhook but nothing works. I'm not sure where to begin troubleshooting this or if I can even do anything about it. I couldn't find a way to contact Prismic either. Any guidance would be much appreciated.

Hello @diegovogel

Welcome to the Prismic community. Could you please send me your Repo URL so I can dig into it? You can send me a private message too.