Cannot read cookies written from javascript

The javascript cannot read cookies written using document.cookie.
The session can be read by console.log(document.cookie), but when I restart the browser(firefox), the result of console.log(document.cookie) becomes empty string.
You have configured max-age and the developer tool confirms that cookies are stored.

Even though the cookie is saved, if the session is switched, the document.cookie will not be able to read it.
I would appreciate it if you could provide me with a solution.

function cookieWrite() {
document.cookie="cookie=test;max-age=2592000";
}
function cookieRead() {
console.log ( document.cookie);
}