PayPal provide 2 ways of payment:

First: Manual payment where customer has to press pay button in his unpad invoice monthly to activate / trigger payment. In this case system cannot get money automatically from PayPal.

Second: Automatic payment where system communicate with PayPal and get payment without manual trigger from customer.

To activate automatic payment / subscription, press on subscribe button when you pay your invoice then system will get money automatically for any future invoices related to this specific product / service

Please note that system will automatically cancel the subscription from PayPal when the service get terminated