Customers are getting a message saying they have already signed up when they try to register. Promo codes are being created which I can see in the back end, but they are not being sent to the customers
My best guess is the reason they are seeing that message is because they are entering their info twice. I would guess this is because they are not getting the promo codes the first time.
If you see the email in your list then it must have worked at least at the most basic level.
Regardless I have a solution to try.