If you have setup your website to use SSL but still getting the Not Secure message when visiting your website then there will be some files like images, css or js etc that don’t have the “s” in their URL address.
To help identify the insecure files, open your website using Google Chrome web browser on your PC, then right click on the page, then click Inspect. Then in the window that opens click the Console tab. You can then get some information on that page about the insecure file URL addresses and their location on your website.