PemBer's Paypal IPN Url is <your-forum-url>/pember_callback.php So for eaxmple for this site it is: http://paidmembers.net/pember_callback.php If you have xenforo installed in a subfolder it will be: <your-forum-url>/subfolder/pember_callback.php You will have to do this step in order to make sure your recurring payments extend your member's upgrade. The reason this step is required is that Paypal doesn't allow to programatically set NOTIFYURL when creating a recurring payments profile through the API. Login to your Paypal Business or Premier Account and click on Profile. Once there, click on My Selling Tools -> Instant Payment Notifications -> Update If you have not done this before you will have to click a button which says "Choose IPN Settings" Now enter the url <your-forum-url>/pember-callback.php in the field. And Click on Save That's ALL!