I had this working earlier, but I've had a bit of a time today and went through a number of steps to solve another problem I was having that involved replacing salts/hashes in wp-config. Possibly as a result of this, or possibly because of SSL issues I was having, users are now being forced to log in again when attempting to purchase domain mapping through Pro Sites. The login is always unsuccessful, and leads them to yet another login page, where they are asked to do math problems repeatedly. Can someone help? Access to my site is open for staff.