Google Map element requires the Google Map API key to get things started there. It is required to authenticate the requests associated with the project for usage and also acts as a unique identifier for the billing account.
Give below are the steps to generate the API key:-
1. Open the link attached, and given below is the field provided for adding the key in the JD Builder configuration page. (link here)

Google Map API Key field
2. Go to the Project Selector page and create a new project.

Create a new project
Fill in the details required.
3. After creating your project go to APIs & Services > Credentials.

Go to Credentials

Listed API Key is here
There you will see your newly created key listed on the credentials page, under API keys.
4. After creating the key go to Library.

Make sure to Enable Map API key

Enable the API
And then click on Maps JavaScript API. Here you have to enable the map API for the key to work.
5. After enabling the Maps JavaScript API, enable the Places API too.

Make sure to enable the Places API

Enable Places API
6. Copy & Paste the Map API Key.

Add the key in the field
Now just copy and paste the API Key in the field provided on the configurations page and you are good to go.
7. One last step, you need to enable billing on your key to use Google Maps.
Google has implemented pay-as-you-go-pricing for its product which means you need to enable billing on your account to use Google maps. You can do that by going here and read about the same here.