Cronjob not firing function within class that extends WC_Email

I’m really frustrated right now, because I just can’t seem to figure out what’s wrong here. Maybe it’s something really simple and I’m just stuck somewhere. Please help me out!

I’m working on a small plugin to add a payment reminder to WooCommerce. I added a wp_schedule_event (nd_payment_reminder) to the activation hook. This works so far.

In my main plugin file I’m including my class which looks a little like this:

class ND_Payment_Due extends WC_Email { public function __construct() {         parent::__construct();         add_action('nd_payment_reminder', array($  this, 'getOpenOrders')); }  public function getOpenOrders() {         // getting data and triggering the email } [...] } 

Whatever I try, the function getOpenOrders seems not to be started. I’ve copied this plugin from another website where I originally used it and it still works there – so I’m really confused right now.

I tested it from the functions.php – this works:

add_action('nd_payment_reminder', 'testfunction'); 

I also thought my getOpenOrders()-Function might be faulty, but even when I use another simple function from within my class it’s just not working. 🙁

Any ideas would be highly appreciated! Thanks in advance!