Support

That feature will convert all instances of http:// to https:// in the content. It does that by hooking on the onAfterRender event of Joomla!. This has some important consequences:

• It is possible for another plugin to register itself as the last onAfterRender handler. This is what Admin Tools itself does. If another plugin does that after Admin Tools has registered itself then the content generated by the other plugin cannot be converted.
• If you have Joomla! cache turned on or the Joomla! page caching plugin enabled then this event won't be triggered when a page is served from the cache. Clearing the cache, Joomla! and browser, is in order.
• It works on the HTML content, not the response headers. If you have a redirection it won't be converted to HTTPS.

Also, there's one major caveat with this Admin Tools feature. It will only work when Joomla! itself reports that the current site's URL starts with https://. There are two reasons why this may not be true:

• The $live_site parameter in configuration.php is set to a plain HTTP URL. This means that Joomla! always sees an HTTP URL, even when you access the site over HTTPS.
• $live_site is not set but, for any reason, your web server reports a plain HTTP URL. I've seen that happening on one of my dev sites when I tried setting up a self-signed wildcard certificate (and only for the default index page of the site) but my Apache knowledge stops short of solving that and, frankly, I didn't have the time to dig deeper.

If I were to take a wild guess, I'd say that either of the last two issues may be what is going on with your site. That would explain why you have HTTP links on it despite switching to HTTPS. Check your live_site and if this doesn't help you need to contact your host to verify your HTTPS setup.