IPN (Paypal payment notification url)

[julianf]

I need to know where can I find the IPN (Paypal payment notification url) URL since the payments made by Paypal and according to the notification sent to us is not working:

I have a page in Prestashop and there are bugs with payments with Paypal, so inform me to communicate with the Server facilitating the following information: "Please check your server that handles PayPal Instant Payment Notifications (IPN). IPNs sent to the following URL(s) are failing:

https://null/www.azulcafetogo.com/es/module/paypalusa/validation?pps=1

If you do not recognize this URL, you may be using a service provider that is using IPN on your behalf. Please contact your service provider with the above information. If this problem continues, IPNs may be disabled for your account."