Enhance troubleshooting details for webhook delivery errors (#58741)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: grmtek

content/webhooks/testing-and-troubleshooting-webhooks/troubleshooting-webhooks.md

@@ -46,10 +46,12 @@ To deliver webhooks to your local server for testing, you can use a webhook forw
 
 ## Failed to connect to host
 
-The `failed to connect to host` error occurs when {% data variables.product.company_short %} attempts a webhook delivery but could not resolve the webhook's URL to an IP address.
+The `failed to connect to host` error occurs when {% data variables.product.company_short %} attempts a webhook delivery but could not resolve the webhook's URL to an IP address or there are network restrictions preventing connection to the host.
 
 To check whether a host name resolves to an IP address, you can use `nslookup`. For example, if your payload URL is `https://octodex.github.com/webhooks`, you can run `nslookup octodex.github.com`. If the host name could not be resolved to an IP address, the nslookup command will indicate that the server can't find the host name.
 
+You should make sure that your server allows connections from {% data variables.product.company_short %}'s IP addresses. You can use the `GET /meta` endpoint to find the current list of {% data variables.product.company_short %}'s IP addresses. See [AUTOTITLE](/rest/meta/meta#get-github-meta-information). Ensure connectivity is allowed from the IP addresses listed in the `hooks` section. {% data variables.product.company_short %} occasionally makes changes to its IP addresses, so you should update your IP allow list periodically.
+
 ## Failed to connect to network
 
 The `failed to connect to network` error indicates that your server refused the connection when {% data variables.product.company_short %} attempted to deliver a webhook.