At times, you will see HTTPS on the home page. However, when you will go to any static page, it will show the page is unsecure. Although the SSL certificate is installed successfully, you may see this error.
When you are facing this issue on the static page, then you can console check that page and replace the content that is causing the issue. For example if the image used in your page is causing the issue, then the image tag on your product page will look like:
http in there means that the image is NOT served securely. So, to resolve this issue you could use any of the following to serve the images securely:
Now, the explicit
https will always serve the image securely even when the page is not served securely. While relative linking will serve the image securely only if the page is served securely.