notification via email

once the user registers from the front end using profile builder registration form, a notification is displayed on the same page saying that “Before you can access your account test@gmail.com, an administrator has to approve it. You will be notified via email.” but this notification is not sent via email, that is as per the plugin feature, the user should be notified that his registration is pending and is waiting for admins approval, this email is not getting sent to the user, whereas he admin is notified with the email regarding the new users sign up. once the admin approves or disapproves the new user,the user is notified via email, this feature of the plugin is working perfectly fine. please can you let me know what is going wrong and suggest the appropriate solution. thanks in advance.

https://wordpress.org/plugins/profile-builder/