Cannot access Updates & Upgrades page: ERR_CONNECTION_TIMED_OUT

Symptoms

• Cannot open the Updates & Upgrades page:

  CONFIG_TEXT: This site can’t be reached
  ERR_CONNECTION_TIMED_OUT

• Updates & Upgrades redirects to https://example.com:8447;
• The https://203.0.113.2:8447 is opening successfully;
• CloudFlare is used:

  # dig +trace servername.com
  
  ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.62.rc1.el6_9.2 <<>> +trace servername.com
  ;; global options: +cmd
  ...
  servername.com. 172800 IN NS john.ns.cloudflare.com.
  servername.com. 172800 IN NS dell.ns.cloudflare.com.
  ;; Received 173 bytes from 2001:500:d937::30#53(2001:500:d937::30) in 100 ms
  servername.com. 300 IN A 104.18.50.15 <<<< CloudFlare IP address
  servername.com. 300 IN A 104.18.51.15 <<<< CloudFlare IP address
  ;; Received 65 bytes from 2400:cb00:2049:1::adf5:3bb9#53(2400:cb00:2049:1::adf5:3bb9) in 98 ms

Cause

Incorrect CloudFlare settings.

Resolution

Check the CloudFlare settings. Contact CloudFlare support for more information - https://support.cloudflare.com/