How to register and add Google Maps API key?

If your Google Maps stop working on your website recently or you get the following error:

Oops! Something went wrong.
This page didn’t load Google Maps correctly. See the JavaScript console for technical details.

and you didn’t register your API key yet then:

• Please follow the instruction from here: https://developers.google.com/maps/documentation/javascript/get-api-key#key and register new API key for your domain.
• Go to WP Dashboard > Appearance > Customize > Maps and put your API Key you registered in step 1. If you can’t find Customize > Maps in your WP then please make sure that you are using the latest version of the theme and update if necessary.

Save changes, refresh browser and plugin cache (if used) and your map will work again.