Please help...what did you do to get it working? I have similar problems.
I am using 1.6.4 and can not get Paypal to work. I have set up my Paypal using Auto Return On, IPN On and PDT On, plus tried all combinations of these. Do I need an API certificate from Paypal? Paypal takes the money and sends an email to both student and site. Auto redirects make to Moodle site, but student is not enroled. Standard message received. I've tried all varieties of user and site settings without success. The firewall has been disabled, so it's not that. In all cases the standard message is received:
"Thank you for your payment! Unfortunately your payment has not yet been fully processed, and you are not yet registered to enter the course "Course Name". Please try continuing to the course in a few seconds, but if you continue to have trouble then please alert the Instructor or the site administrator "
Just what settings do I have to make. You say that you set the User and Autentication settings to default? Which settings, where, and does that work for 1.6.4? The documentation in this area is very poor - please, please help! On-line payment is essential for our site. If Paypal does not work then I'll have to stop using Moodle in total - which I don't want to do (apart from sending 6 months work down the drain!).