Google Maps requires you add your own API key before you start using it.
This is a copy from Google Maps official announcement:
As of June 22, 2016 we are making the following changes to the Google Maps APIs Standard Plan: We no longer support keyless access (any request that doesn’t include an API key). Future product updates are only available for requests made with an API key. API keys allow us to contact developers when required and help us identify misbehaving implementations
API is added in Theme Options – Google Maps settings.
Select – GET A KEY
Click Create and Enable API
Copy the API and go to API Console
Copy the key in theme options and save.