Some of the sign-up notifications are getting caught in spamtraps. You can check your spam or junk mail folder to see if the notice is there. You should also add chowhound.com to your allowed senders list so that you'll receive future notices. We may need to communicate with you about, for example, a deleted post.
If you've checked your spam filters and you still don't have the email, it may have been filtered farther upstream by your ISP, or you may have entered an incorrect email address.
In that case, please send an email to moderators@chowhound from the email address you used to register. Include your username (but not your password!) in the email. We'll try to help.