The JetPack server was unable to communicate with your site
If you have received the following error message when trying to install or use Jetpack,
Your website needs to be publicly accessible to use Jetpack: site_inaccessible
Error Details: The Jetpack server was unable to communicate with your site [HTTP 403]. Ask your web host if they allow connections from WordPress.com. If you need further assistance, contact Jetpack Support.
It is because you Hosting provider disabled access to your xmlrpc.php script by default. They have this disabled because attackers have the ability to brute force as well as send out attacks using an exploit against the pingback ability. (Read More)
FYI: What is XML-RPC?
XML-RPC.php is a file dealing with the Remote Procedure Call or RPC on your server, and it is crucial for a WordPress website to functional properly. It allows the operating systems running in a different environment make procedure calls over the Internet, here procedure calls means that there exists a software in another corner of the Internet web and is calling a function of another software in some remote location. There are functions in it that are helpful in writing XML-RPC clients and servers. Apart from that there are several functions in it which you can use. Check out the complete list here.
Here my XML-RPC.php file wasn’t properly receiving the traffic it should and so Jetpack resulted in this error.
To enable access to your xmlrpc.php we first recommend upgrading WordPress to the latest version along with installing a plugin that will disable certain functionalities of the script that may potentially allow an attacker to use them maliciously. The plugin is available here.
Using FTP or File Manager browse to your public_html folder and inside open the .htaccess file. Once opened, add the following rules to the top.
# Whitelist Jetpack/ Automattic CIDR IP Address Blocks
Allow from 22.214.171.124/18
Allow from 126.96.36.199/16
Allow from 188.8.131.52/17
Allow from wordpress.com
Deny from all
Save and your xmlrpc.php script will once again be reachable by Jetpack 🙂