Subscription Fault

I have read through many of the posts in here about the "Subscription Fault" issue but, none are the same issue I am having.  I have a production site and a staging site.  My staging site works perfect.  My production site only partially works and is an clone of staging.  My emailing within the sites works.  The issue is I cannot get subscriptions working in production.  I have looked at both sites they setup the exact same way.  I have read that the Subscription Fault is an indication of someone trying to register for a second time with same email.  That is not my case.  I have tried using an alternate email and still get the error.  Again it all works in my staging site but, not the production.  People can post comments and get an email response.  What else should I look at?