When you first add our HTML embed code to your website, you may see the error message “MissingKeyMapError” in your browser's debugging console. This error may also appear if you add your existing store locator to a new domain.
This is due to a change in June 2016 which Google made to the Google Maps API terms of service which now require that you create an API key and include it on pages on your site that use Google Maps.
You can find a quick guide to creating an API key (don't worry, it's free and takes only a few minutes!) and including it with your store locator here.