title: Paypal Plus and Webhooks won't fire
body: <p>I am working on integrating Paypal Plus with Webhooks into my Ruby on Rails App using the PayPal-Ruby-SDK.
  So far everything is working, expect for Webhooks in Sandbox mode. I have setup my App in the developer dashboard and configured a Webhook to listen on all Events. Under Webhook Events i can see the event type "Payment sale completed" as expected but the event never reaches my app. When I use the Webhooks Simulator my App does recieve the event so the communication seems to be working. In the status column under Webhook Events in the Dashboard there is a yellow exclamation mark but with no further information what went wrong. Any help would be appreciated</p>