If you installed nginxcp to boost your cPanel server performance, then you might have noticed that Munin has stopped monitoring Apache. This is because nginxcp changes the Apache port to 8081, and Munin can't fetch the required information from the Apache server-status page.
To fix it, open the file:
and add the following code:
[apache_*] env.url http://127.0.0.1:%d/whm-server-status?auto env.ports 8081