The Google Maps APIs require an API key for new domains as of today. See announcement: http://googlegeodevelopers.blogspot.com.au/2016/06/building-for-scale-updates-to-google.html
To fix this:
1) Create an API key as per instructions here: https://developers.google.com/maps/documentation/javascript/get-api-key
2) Edit the line in the plugin that loads the Google Maps API to include your key as the value of a ‘key’ parameter. Wherever you find “https://maps.googleapis.com/maps/api/js” or “http://maps.googleapis.com/maps/api/js” in the plugin, change it to “https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY”.
