One thing that is often the case is that test sign-ups are with email addresses that are already signed up to your email list.
Also be sure you have a List Selected!! By default it will say "-- Don't push to list --". If you do not select a list, the emails will not pass. Select a List and then click SAVE. :)
If an email address is already signed up, we won't re-sign it up and we won't save it within the app either.
Definitely give it a shot with an email address you're sure is not on your list already.