Sometimes during install things go wrong, when this happens the configuration might not be completed. Have a look at the default configuration here and make sure that your file contains the same rendertasks and basic settings.
This is the defualt newsletterStudio.config file:
Newsletter Studio can also use the members of the site as receivers of an newsletter. When the newsletter is going to be sent, just choose one of the Member Groups in the list.. Letting the user ignore newsletters By default Newsletter Studio will send the newsletter to all the members of a certai…