Two Google keys: client restricted by referrer, server restricted by API
One key the browser can see, locked to your domain. One key the server uses, locked to five APIs.
PROCEDURE: 1) Google Cloud console with a billing-enabled account; 2) new project named after the Bubble app; 3) Library -> enable Geocoding API, Places API, Geolocation API, Maps JavaScript API, Time Zone API; 4) Credentials > Create credentials > API key -> rename 'client' -> Application restrictions: HTTP referrers -> add the app URL with a trailing * (or the custom domain); 5) second key 'server' -> API restrictions -> the five APIs -> Save; 6) Bubble Settings > General: server key into 'Google geocode API key', client key into 'Google Map API key'; the warning icon clears. Up to five minutes to apply. Not free - billing must be linked.
Without it the map element and location search silently fail.