Hi
Presuming that you have set the news as "subscibable" within news managment, the error is probably a fault in your database.
Check, using phpmyadmin, that the "is_news_subscribeable" flag is not empty.
Also, please update your signature - you say you are on 4.0.14 - but you actually are using v17. Each version is different, has different bugs and problems - thus different fixes and answers.
