that does not seems right
there is no such a thing as Slim\Middleware\HttpNotFoundException nor this is throwed in RoutingMiddleware on this line (there is Slim\Exception\HttpNotFoundException )
what version of Slim exactly you are using (by composer.lock file?)
maybe I would suggest delete vendor folder and run composer install again
Custom project I using composer.
personal project test:
Index:
<?php
session_start();
require_once 'vendor/autoload.php';
use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Message\ServerRequestInterface as Request;
use GA\PageAdmin;
use GA\DB\Sql;
use GA\Model\User;
use Slim\Factory\AppFactory;
$app = AppFactory::create();
$app->addErrorMiddleware(true, true, true);
require 'functions.php';
require "site.php";
require 'cpanel.php';
$app->run();
?>