I’m sorry, I see you might have misunderstood me calling it “on-site” payment. What I mean is on arrival payment. The booking system does not offer any other payment method, the customer is only allowed to select payment on arrival (but as meantioned earlier, the booking system uses coupons, and therefore has to include the payment step of the booking – please correct me if this is wrong, and there is another way for a customer to add a coupon code).
So, this might be the reason then for the payment notifications not being received. A payment transaction is what pushes the system to send these e-mails?