You are supporting a webhook delivery pipeline for a B2B SaaS product. A client reports that payloads are not reaching their server, and the issue may be in the sender, the retry path, or the client endpoint. You need to isolate where delivery is breaking and determine whether the failure is transient, configuration related, or caused by bad payloads.
Walk me through how you would troubleshoot a webhook that is failing to deliver payloads to a client's server.