Cookie not saving

[dannon]

Hello, I am working on a login system for my website, more specifically the remember me feature. I have made it so my PHP script saves an authentication token as a cookie, and then encrypts the token and then saves the encrypted token into a database when the user logs in.
If the cookie is already set and there is no session, the application will validate the cookie and then generate a new token and then log the user in.
 
I have tested the remember me feature by removing the PHPSESSID, to check whether or not the remember me feature will use the cookie correctly to log me back it. However, I have noticed that sometimes the cookie would not update, thus causing me to stay logged out and preventing me from logging in again.
 
Is there a way to fix this?
 
If you are wondering, here is my code that updates the token: 
 

public function updateCookie($username) {
        $randomString = $this->generateString();
        setcookie("rm_session", $username . "-" . $randomString, strtotime('+1 month'), "/");
 
        Model::$db->preparedQuery("INSERT INTO remember_auths (username, token) VALUES(:username, :token)", array(
            ":username" => $username,
            ":token" => $this->cryptString($randomString)
        ));
    }
 

I am also trying to make the cookie HTTP only; however, for some reason it is not letting me to set a domain, every time that I set a domain, the cookie doesn't show up. It's most probably because I am using the RewriteEngine. Is there a way to fix this aswell? I have tried using the domain as localhost, null, false and 127.0.0.1, but it didn't work.