In this day and age browsers now default to using https:// instead of http://. We make SSL available to all of our clients for free with Let's Encrypt SSL. As a result of this, it is important to make your content surface-able via https:// by not using http:// in your code when you link to pages, images, .css, .js, .etc
An easy way to track the offenders is to view your source and perform a search for http:// and change those over to https:// in your code.
You may also create an .htaccess in your public_html directory with the following contents:
RewriteEngine On
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://www.yourdomain.com/$1 [R,L]
which will redirect any request for http:// to https://
If you are using WordPress, installing the Really Simple SSL plugin makes life a lot easier for this. Once it is installed set your WordPress settings to point the domain to https:// instead.