The problem seems to come from this file :
/buddypress/bp-groups.php
which calls do_action( 'groups_promoted_member', $user_id, $bp->groups->current_group->id );
before the file below is included
/buddypress/bp-groups/bp-groups-notifications.php
that should add the action to add the notification: add_action( 'groups_promoted_member', 'groups_notification_promoted_member', 10, 2 );