Set Google API Key in functions.php (Wordpress) From https://support.advancedcustomfields.com/forums/topic/google-maps-field-needs-setting-to-add-api-key/
// enqueue scripts and styles
function nr_load_scripts() {
wp_register_script('googlemaps', 'https://maps.googleapis.com/maps/api/js?key=XXX',null,null,true);
wp_enqueue_script('googlemaps');
}
add_action( 'wp_enqueue_scripts', 'nr_load_scripts' );