How to validate my endpoint url in Zoom


I want to overtake Zoom Event ticket data to my active campaign Account.

Therefore, I need to have a Zoom App (in Zoom Marketplace).
And I need to have a webhook in scenario.

Second one I have created and I also have an Endpoint URL.
But now I have to validate this Endpoint URL in Zoom. And this is failing all the time.

Webhook in

App in Zoom Marketplace

** Scenario on to respond to Zooms validation request**

OK, an now I have read this document (-> Using webhooks) to understand how to respond on a Zoom endpoint validation request. I did it in the JSON module. And respond it in Webhook respond module.

But the validation still fails. And I can’t figure out why.
Is there a way to debug this issue?