I think you are banned because yahoo answers are very strict now in answers. If they saw your answers are spam they will give you warning or worst your account will be banned.
Do you mean , the links from Yahoo answer is not used to pass link juice to your website? or you are unable to put your links there ? Yahoo answers use nofollow to the links so it cannot be used to get more PR for your website (I hope the nofollow issue was your question).