It just happened tome too: blank screen. Browser console says:
You have exceeded your daily request quota for this API. If you did not set a custom daily request quota, verify your project has an active billing account: Google Maps Platform - Location and Mapping Solutions For more information on usage limits and the Google Maps JavaScript API services please see: Maps JavaScript API Usage and Billing | Google for Developers
Says it all, doesn´t it: you need to get your own API key.