If the plugin does not detect SSL, but you are sure you have SSL, it is possible the plugin could not open the test page, which is used to check if SSL is active. This might be caused by a security setting on your website, or of your server.
You can doublecheck your certificate by doing a scan on ssllabs.com/ssltest. It that checks out, you can bypass the Really Simple SSL certificate check in three steps:
- In your browser address bar, change the url to https, and hit enter
- Your site layout might break, but don’t worry. This is because the stylesheets are not SSL yet.
- Look for the button “enable SSL”, and click it.
Your site will now be configured for SSL.