If you have SSL but some browsers on your Android device say that your site is insecure, you should know that this is not caused by Shield. 

Basically, 1 of your plugins and themes is not including images/JS/CSS using a secure URL.  To find the culprit, test all plugins by disabling a plugin 1 at a time (or switch theme) until the problem disappears. Then you'll know you've found the plugin(s) causing it.