Custom Endpoint not working in Multisite

I’m using WordPress sample code for adding custom endpoint to rest api from Add Custom Endpoints in WordPress Rest API Handbook:

function my_awesome_func($data) {
    $posts = get_posts( array(
        'author' => $data['id'],
    ) );
    if ( empty( $posts ) ) {
        return new WP_Error( 'no_author', 'Invalid author', array( 'status' => 404 ) );
    }
    return $posts[0]->post_title;
}
add_action( 'rest_api_init', function (){
    register_rest_route( 'myplugin/v1', '/author/(?P<id>d+)', array(
        'methods' => WP_REST_Server::READABLE,
        'callback' => 'my_awesome_func',
        'permission_callback' => '__return_true',
    ));
});

but it returns rest_no_route (404) in multisite:

http://newsut.ir/wp-json/myplugin/v1/author/1

Same code in another site (not multisite) works correctly:

http://z-design.ir/khelo/wp-json/myplugin/v1/author/1

Multisite .htaccess file:

RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^wp-admin$ wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^(wp-(content|admin|includes).*) $1 [L]
RewriteRule ^(.*.php)$ $1 [L]
RewriteRule . index.php [L]
Options -Indexes