I checked my wordpress install with the url followed by /xmlrpc.php and you should see the following: XML-RPC server accepts POST requests only.
If you are getting a “404 not found” make sure that the file exists in the main directory of your Wordpress install as shown in cPanel > File Manager
Refer to this guide for the steps to check.
This file is used by Jetpack and other plugins and apps to connect to your site. It must return the following message:
XML-RPC server accepts POST requests only.
You can see a working example here:
Since your site returns a 404 error for this page, I would recommend that you check the following:
Can you see the /xmlrpc.php file at the root of your WordPress installation when accessing your site via FTP? If you don’t, then please try re-installing WordPress. You can do this by going to the Dashboard -> Upgrades page, then click the “Reinstall WordPress” button.
Do you use any security plugins that may block access to this file? If so, could you try to disable them? You might also want to check your site’s .htaccess file for any rules that might be blocking access to the xmlrpc.php file.
Does your hosting provider block access to this file? If you don’t find any plugin that may block access to the file on your site, I would recommend that you get in touch with your host.
For question 3, my test site is not blocking xmlrpc.php that I can find, but it’s possible to do so in the .htaccess in some cases. So please check for xmlrpc.php references in the .htaccess file in the main Wordpress Directory.
If after checking for the xmlrpc.php file and looking at the .htaccess file you are still having problems, please create a support ticket in your Client Area or contact firstname.lastname@example.org