Error from park wrapper: domain.com is already configured

On a cPanel server if you get the error: Error from park wrapper: domain.com is already configured while adding an add-on domain under cPanel. Make sure to remove the domain.com entries from:

/var/named/domain.com.db

/etc/httpd/conf/httpd.conf

/var/cpanel/users/username

/etc/userdomains

/etc/localdomains

Renaming or commenting will not help; you will have to remove the entries completely. Try now.

This worked for me.