Custom Endpoint shows 404

Hi,
I am stuck on creating custom endpoints. I followed this tutorial to create custom endpoints. But, it always returns 404.
https://developer.ww.wp.xz.cn/rest-api/extending-the-rest-api/adding-custom-endpoints/

I added code below to function.php

add_action('rest_api_init', function() {
  register_rest_route('awesome/v1', '/awesomeparams', array(
    'methods' => 'GET',
    'callback' => 'get_awesome_params',
    'args' => array(),
    'permission_callback' => function () {
      return true;
    }
  ));
});
function get_awesome_params( $data ) {
    return "aaaa";
}

When I trying to access: http://smap.cas.mcmaster.ca/wp-json/awesome/v1/awesomeparams

It shows 404:
404 error

I also tried to flush the permalinks by going to WordPress admin -> Settings -> Permalinks and click save.

Can I get some help?
Thanks a lot!

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