I installed Q&A plugin on my site, and then I changed my

Hello,
I installed Q&A plugin on my site, and then I changed my wp-config.php in order to modify the slugs/urls, but it doesn't work and the slugs still beeing the same.
My wp-config.php :

define(‘QA_SLUG_ROOT’, ‘consultas’);

define(‘QA_SLUG_ASK’, ‘preguntar’);

define(‘QA_SLUG_EDIT’, ‘editar’);

define(‘QA_SLUG_UNANSWERED’, ‘no-respondidas’);

define(‘QA_SLUG_TAGS’, ‘ciudad’);

define(‘QA_SLUG_CATEGORIES’, ‘especialidad’);

define(‘QA_SLUG_USER’, ‘usuario’);

I would like to change it. I'm doing something wrong?

Thank you,
Isabel