In file lfs_paypal/listeners.py in function mark_payment, when LFS_SEND_ORDER_MAIL_ON_PAYMENT=True it calls mail_utils.send_order_received_mail(order).
But that function required 2 parameters and you pass only one to it. So the mail is not sent and the error occurred.
In file lfs_paypal/listeners.py in function mark_payment, when LFS_SEND_ORDER_MAIL_ON_PAYMENT=True it calls mail_utils.send_order_received_mail(order).
But that function required 2 parameters and you pass only one to it. So the mail is not sent and the error occurred.