It is quite common a client or even myself not being able to access my website. This is caused because mistakenly the mod_security (a module installed at linux servers to secure your website against malicious users) has placed the IP address at the deny list after thinking it is a suspicious IP. The way to remove it and have access to your site again is:
1) Locate the file: /etc/apf/deny_hosts.rules
2) Remove your IP
3) Restart apf: apf –restart
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