Automatic Affiliate registration not working

I have affiliate registration set to automatically accept new affiliates. However, the newly-registered affiliate is not receiving a confirmation email (though the administrator receives the proper notification), nor is the affiliate added to the affiliates list, or allowed to see their affiliate area. The confirmation email is not in spam, or any other folder. It is simply not being sent. The documentation says nothing about whether that email must be opened for the affiliate to access their affiliate area, and all other responses to this kind of issue suggest only that the email might have gone to spam.

My site is prismanaturalusa.com/affiliate-area

It worked for the first few affiliates, when we tested it before the site went live, then stopped.