I am using PayPal sandbox account to test enrollment using PayPal on my moodle site but when the currency of business account registered to PayPal is USD and the currency for course registration is USD at that time the enrollment is successful but if the currency for course registration is EURO at that time the enrollment is not successful even after PayPal payment is successful.
On the other hand, when the currency of business account registered to PayPal is EURO and the currency for course registration is EURO/USD at that time the enrollment is successful after PayPal payment is successful.