Alan,
I had problems testing Paypal in 2.3 too. The problem I was getting was due to my site being local/inaccessible from PayPal. Once I visited and used my Moodle install on an actual live web address the enrollment went through.
Enrolment
HELP! Paypal not working in 2.3
Denne diskusjonen har blitt stengt, og du kan derfor ikke svare i den lengre.