Ah, got the notification of your comment here. But nothing on cookbooks and recipes. :-( In fact, I think it's been over a year, since I had one of those, unless they come with a different email address.
I remember that we had to sign up seperately for the forum, which could mean that you used two different email addresses - but given that you're assumingly using your email address to login to Cookbooker the problem is probably not that the notifications are going to a wrong email address. I'd rather guess they've been turned off/ceased to work.