I checked your site with HTTPS and I see a green lock, which means the SSL itself is working. But when I visit your site without SSL, I don’t get redirected to the HTTPS version. That’s likely why you get the warning on your phone.
If you’re using WordPress, the Really Simple SSL plugin should be able to do that. Note that you may need to open your website with HTTPS yourself to convince the plugin that HTTPS is in fact installed.
If that doesn’t work, you can also just set the .htaccess rules by hand to force HTTPS redirects, as we’ve documented here: