You can use your web browser to help identify why your website is saying “Not Secure” even after you have setup your website to use SSL. Usually it will be some images or css or javascript files etc that are being called insecurely. You need to change those insecure resources to use https in their URL’s instead of http.
Using Google Chrome
► Open your website in Google Chrome
► right click anywhere on the page
► click Inspect
► click the Console Tab in the window that opens
You will then be presented with some information about the insecure images and resources on your web page. Use that information to locate where the resources are on your website, then go and edit your website pages and add https to those insecure images and resource files.