Hello robrob11,
First of all, check out the mail function works well in your WordPress.
Did you get any email from your website? New comment, etc.
The second option to temporary disable all the other plugins and try out the signup form again. If it is works, then any of your plugins causing conflict. You can find out which one, just reactive the plugins one-by-one.
If it still doesn’t work, change to theme to any default theme just for a quick test. If it is works, then the theme causing the issue.
By the way, just checked the plugin on my website with a new install and it is works well. Therefore I’m sure it will be a conflict only with your theme or with any of your installed plugins. Another possibility is the lack of mail() function as I mentioned above.
If the problem still exists, please send me your website URL and I’ll check it directly on your website.