If you are having trouble with your URL showing as not secure lets first go to https://mxtoolbox.com/DNSLookup.aspx type in your URL and search to make sure that your URL is pointed to only Customer Engine. 

If you see a IP address that isn't associated with Customer Engine you will need to go into your registrar and dns settings and remove the A record associated with the IP address that is not Customer Engine. 

If your A record is set up correctly and you are not showing any other IP address associate with your URL please send your URL to support for us to take a look.