1. The CNAME hasn't been set up correctly. This can be checked by running the domain through https://www.dnswatch.info/ and getting a response where the CNAME is not pointing to www.cmsappbuilder.com
  2. The CNAME is correct only you've entered the wrong Custom Domain in the Reseller Settings. In the Custom Domain field, enter your custom URL (without http://) The Subdomain field can be left empty.