That error sounds like your Shotgun site cannot reach the event service. Can you check our documentation here for IP allowed list for Webhooks? There are three additional IPs that you’ll need to add to your Allowed IP list in your Site Preferences:
I’ve been talking to the engineers about what could potentially cause this. It sounds like there was a URL change on your site, which led to capital letters in your URL name. Typically, we catch instances like this automatically, but it looks like there was a loose end in the internal tools which our team use to change site URLs. This is what’s causing the issue with webhooks.
The good news is that the fix is easy - I’ll just need to change your site URL to the same as it is now, but with all lowercase letters instead of capitals. I’ll open a Zendesk ticket with you, so we can discuss the details there, outside of the public forum.