You are running Apache2 web server on port 80, which is interfering with the Pi-Hole web server (lighttpd). You will need either to uninstall Apache2, or move either Apache or lighttpd to a different port so they don't conflict with each other.
*** [ DIAGNOSING ]: Dashboard and block page
[✗] Block page X-Header: X-Header does not match or could not be retrieved.
HTTP/1.1 302 Found
Date: Sun, 01 Sep 2019 17:38:18 GMT
Server: Apache/2.4.6 (CentOS) PHP/5.6.40
X-Powered-By: PHP/5.6.40
Location: http://84.80.59.120/
Content-Type: text/html; charset=UTF-8
[✗] Web interface X-Header: X-Header does not match or could not be retrieved.
HTTP/1.1 200 OK
Date: Sun, 01 Sep 2019 17:38:18 GMT
Server: Apache/2.4.6 (CentOS) PHP/5.6.40
X-Powered-By: PHP/5.6.40
Set-Cookie: PHPSESSID=e1uofchg7sgabmqb3rtnif0tq6; path=/
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
Content-Type: text/html; charset=UTF-8