Once a webhook is created, you can view the list of all the deliveries to the endpoint.
In the list of webhooks in Settings -> Manage webhooks, click on any URL to go to the list of deliveries to that endpoint. The deliveries are listed in reverse chronological order of the time they were sent.
The list shows the HTTP status of the response received when the product sent the payload to the endpoint specified in the webhook.
You can click on View Details to open up the exact request and response details of the payload send operation. The details contain request headers, payload sent, response headers and response body.
If you see a delivery with either a status code not present, or a delivery with non-2XX HTTP response code, it means the payload was not delivered correctly because of some reason. It may have been a timeout/unavailability at the API endpoint provided.
If you need to send the same payload to the webhook endpoint for any reason, just click Redeliver in the side pane that opens up on View Details against a delivery.