Just out of curiosity, are they going into your SPAM folder? There's also a chance that your ISP is blocking emails from the site (this is usually dependent on how the mail server is set up). Someone with access to this server would need to verify that the emails are getting sent. They may also be able to tell if the emails are getting "bounced" - although some companies will just "blackhole" any emails that they think are invalid. Then it's up to you to bug your ISP until they fix things. Do you have another email address you could switch to temporarily (just to see if it solves the problem)?
Troy