Paypal Subscriptions Integration

We have a website with a joomla CMS and use Paypal as the payment merchant. We want to automatically create usernames and passwords for users to access our members area when they make a payment through Paypal. We already have this set up, however it doesn't work properly and the usernames and passwords that it creates do not work. We need someone that is skilled with Paypal to be able to fix this for us.