ERROR a2enconf

Hi, ​​After config ln -s ln -s /root/domserver/etc/apache.conf /etc/apache2/conf-available/domjudge.conf Then I type command sudo a2enconf domjudge And I get answer *ERROR : Conf domjudge does not Exist*

I find a post about this error at here: https://www.domjudge.org/pipermail/domjudge-devel/2016-April/001943.html

But I don't know how to fix it by change the permissions. Please help. Thanks!