If you inspect the page using Chrome Developer Tools and then click on the errors/warnings link at top right of console, you will see that it’s due to the Google API link – http://maps.google.com/maps/api/js?sensor=true – containing http. It should be a protocol-neutral link.
Normally you shouldn’t edit a plugin directly but because this hasn’t been updated in 2 years, you may as well. So go into the plugin file and edit themeblvd-google-maps.php. Find the link and either remove the http: (change to //maps.google.com/maps/api/js?sensor=true) or change to https://maps.google.com/maps/api/js?sensor=true – Either should work.
You will also need to go into the plugin file found at /assets/jquery.gmap.min.js to adjust the links found there.
That should do it.
