add troubleshooting ssl cert provisioning in pages (#12030)

* add troubleshooting ssl cert provisioning in pages

* Update content/pages/getting-started-with-github-pages/securing-your-github-pages-site-with-https.md

Some minor rewording of the change suggested by @tcbyrd.

* Update content/pages/getting-started-with-github-pages/securing-your-github-pages-site-with-https.md

Minor rewording.

Co-authored-by: hubwriter <hubwriter@github.com>

Author: djbordelon

content/pages/getting-started-with-github-pages/securing-your-github-pages-site-with-https.md

@@ -37,6 +37,12 @@ All {% data variables.product.prodname_pages %} sites, including sites that are
 3. Under "{% data variables.product.prodname_pages %}," select **Enforce HTTPS**.
   ![Enforce HTTPS checkbox](/assets/images/help/pages/enforce-https-checkbox.png)
 
+## Troubleshooting certificate provisioning ("Certificate not yet created" error")
+
+When you set or change your custom domain in the Pages settings, an automatic DNS check begins. This check determines if your DNS settings are configured to allow {% data variables.product.prodname_dotcom %} to obtain a certificate automatically. If the check is successful, {% data variables.product.prodname_dotcom %} queues a job to request a TLS certificate from [Let's Encrypt](https://letsencrypt.org/). On receiving receiving a valid certificate, {% data variables.product.prodname_dotcom %} automatically uploads it to the servers that handle TLS termination for Pages. When this process completes successfully, a check mark is displayed beside your custom domain name.
+
+The process may take some time. If the process has not completed several minutes after you clicked **Save**, try clicking **Remove** next to your custom domain name. Retype the domain name and click **Save** again. This will cancel and restart the provisioning process.
+
 ## Resolving problems with mixed content
 
 If you enable HTTPS for your {% data variables.product.prodname_pages %} site but your site's HTML still references images, CSS, or JavaScript over HTTP, then your site is serving *mixed content*. Serving mixed content may make your site less secure and cause trouble loading assets.