Wordpress Custom Query Vars with pretty permalinks

Question

I've been wracking my brain with this problem for the past couple of days, looking over all the potential solutions with no success.

Here's what I'm trying to do. I want to create an SEO friendly url for pages that are created from an API. I have created a page called Book Online which lists categories of what they offer: Spa, Acupuncture, and whatnot. When they click on that category, I want it to look like /book-online/category/Spa/. Where /category/ is a child page of Book Online.

BUT, I have to pass Spa's ID and an authentication token.

    add_rewrite_rule(
   '^book-online/category/([^/]*)/?', 'index.php?catID=$matches[1]&catname=$matches[2]&token=$matches[3]',
   'top'
);

function add_query_vars_filter( $vars ){
  $vars[] = "catID";
  $vars[] = "catname";
  $vars[] = "token";
  return $vars;
}
add_filter( 'query_vars', 'add_query_vars_filter' );

I have checked the wp_rewrite rules and I can see that it has been added to the rules, but it's not generating. Can anyone help me?