You can try to get help from where ever you download the module from.
Support for Newsletterpro should come from the author: musox.com/
according to his site: musox.com wrote
....Then I somewhat switched the site's focus as a repository for modules/add-ons for Dragonfly CMS. However, due to events of egos, I will not be supporting/creating any more modules. If there was a download once available here for Dragonfly... check dfbounty.org. Otherwise... you're out of luck.
He is not supporting his own module. It is still avaliable for download on dfbounty, maybe they will help you as he said.
I have a modified version of Newsletter Pro available for download on my site. In a nutshell it is setup to use WeblinksPro and ForumsPro (so if you don't use both of these then it would be pointless to install this) and it may correct the issue you're experiencing.