Why I can't send cookie in Mercure with Symfony?

Question

I make an online auction site and I want the user who previously had the highest bid to be able to receive a real-time notification, when another user has submitted a higher bid than his. So I want to target my user using cookies.

And I tried this:

public function returnNotification(HubInterface $hub, string $message, string $userIdd){
        $userId = Uuid::fromString($userIdd);
        $userIdCookie = new Cookie('user_id', $userId, 0, '/', null, true, true, false, Cookie::SAMESITE_NONE);
        $update = new Update(
            "https://127.0.0.1:8000/instrumenthol",
            json_encode(['status' => $message]),
            true,
            $userIdCookie
        );
        $hub->publish($update);
        return new Response('published!');
    }

And on the client side I get the notification with:

<script>const url= new URL("https://localhost/.well-known/mercure");
        urlToAppend = 'https://127.0.0.1:8000/instrumenthol';
        const eventSource = new EventSource(url,{
            withCredentials: true,
        });
        eventSource.onmessage = (e) => {
            console.log(e.data);
            document.getElementById("message").insertAdjacentHTML('afterend', '<div class="alert alert-success">Ping</div>');
            window.setTimeout(()=>{
                const alert = document.querySelector('.alert');
                alert.parentNode.removeChild(alert);
            }, 50000);
        }
    </script>

My browser recovers the cookie but refuses it, firefox displays the error in the console: GET https://localhost/.well-known/mercure [HTTP/1.1 400 Bad Request 54ms] Firefox can’t establish a connection to the server at https://localhost/.well-known/mercure. firefox error firefox error I don't know how to solve the problem, can you help me solve the problem please?