By default, notifications only work when submitting through the web interface. If you are submitting forms using the REST API, notifications will be ignored.
Solution: Add this code to your functions.php
(Appearance > Theme Editor > functions.php):
/**
* Force notifications when submiting a GravityForm via REST API.
*/
add_action( 'gform_post_add_entry', 'add_entry_callback', 10, 2 );
function add_entry_callback( $entry, $form ) {
if ( 1 === $form['id'] ) {
GFAPI::send_notifications( $form, $entry );
}
}
WARNING
NOTICE: Replace 1
with your form ID.