First of all DNS-records should be checked. Usually for correct work example.org has original IP-address and www.example.org has CDN IP-address and CNAME www.example.org.cybersecurecdn.com . Checking mechanism is described below:

In order to activate alias, a DNS CNAME record for www.example.org needs to be created to point www.example.org.cybersecurecdn.com

Name: www.example.org

CNAME: www.example.org.cybersecurecdn.com

Help link: https://support.google.com/a/topic/1615038?hl=en

How to check? As an example we will use domain name example.org (one of CDN customer).

$ dig A example.org 

;example.org.            IN    A

;; ANSWER SECTION: 
example.org.        3600    IN    A    74.208.236.246 (original IP-address)

$ dig A www.example.org 

;www.example.org.            IN    A

;; ANSWER SECTION: 
www.example.org.        3600    IN    CNAME    www.example.org.cybersecurecdn.com. 
www.example.org.cybersecurecdn.com. 600 IN A    104.37.183.1 (CDN IP-address)

Another way to check DNS settings:

Simple variant

DNS Configuration Analysis

$ nslookup www.example.org
            
Server:        192.168.70.1
Address:    192.168.70.1#53

            
Non-authoritative answer:

            www.example.org    canonical name = www.example.org.cybersecurecdn.com.
Name:    www.example.org.cybersecurecdn.com
            
Address: 104.37.183.1

Such result indicates that customer configured its DNS successfully.  

If resulting lines contain no "canonical name" then try next more complicate variant

  Complicate variant

DNS Configuration Analysis

If above command failed, please, use:

If the command above failed, run (mind abscence of WWW part):

DNS Configuration Analysis

$ dig NS example.org

;; QUESTION SECTION:
;example.org.            IN    NS

;; ANSWER SECTION:
example.org.        172800    IN    NS    ns27.1and1.com.
example.org.        172800    IN    NS    ns28.1and1.com.

dig CNAME www.example.org @ns28.1and1.com

;; QUESTION SECTION:
;www.example.org.            IN    CNAME

;; ANSWER SECTION:
www.example.org.        3600    IN    CNAME    www.example.org.cybersecurecdn.com.

Site availability check is usually performed with such utilities as ping, nmap and telnet and with browser.

If these settings are correct, customer should provide redirect from  example.org to www.example.org