Uncaught Error: Class 'Service\UsersService' not found

Question

I'm trying to run my php-based application, which connects to a mysql DB, launched through docker-compose.

i get this message when i connect to localhost:

Fatal error: Uncaught Error: Class 'Service\UsersService' not found in /var/www/html/dic/users.php:3 Stack trace: #0 /var/www/html/web/index.php(3): require() #1 {main} thrown in /var/www/html/dic/users.php on line 3

user.php

<?php

return new Service\UsersService(
    require "../config/db-connection.php"
);

UsersService.php

<?php

namespace Service;

use Entity\User;
use PDO;

class UsersService
{
    protected $db;

    public function __construct(PDO $db)
    {
        $this->db = $db;
    }

    public function getLastJoined(): array
    {
        return $this->db->query(
            "SELECT id, joined, name FROM user ORDER BY joined DESC LIMIT 10"
        )->fetchAll(PDO::FETCH_CLASS, User::class);
    }

    public function getById(string $id): ?User
    {
        $user = $this->db->query("SELECT id, joined, name FROM user WHERE id = " . $this->db->quote($id))->fetchObject(User::class);

        return ($user === false) ? null: $user;
    }
}

index.php

<?php

$lastJoinedUsers = (require "../dic/users.php")->getLastJoined();

switch (require "../dic/negotiated_format.php") {
    case "text/html":
        (new Views\Layout(
            "Twitter - Newcomers", new Views\Users\Listing($lastJoinedUsers), true
        ))();
        exit;

    case "application/json":
        header("Content-Type: application/json");
        echo json_encode($lastJoinedUsers);
        exit;
}

http_response_code(406);

I appreciate any help!!