Javascript not making cookie

I am working on Salesforce marketing cloud.

I have created a chrome extension using JavaScript. What it has to do is , when user enters username and hits “Next” button , it has to copy the value of Username and create a cookie

The url is https://mc.exacttarget.com/cloud . when you enter it , it navigates to “https://mc.login.exacttarget.com/hub-cas/login%5C*

I have 2 files

Manifest.json :

{
    "manifest_version": 3,
    "name": "SFMC Login Tracker",
    "version": "1.0",
    "description": "Stores the username in a cookie when a user logs into SFMC.",
    "permissions": ["cookies", "scripting", "activeTab"],
    "host_permissions": ["https://mc.login.exacttarget.com/hub-cas/login*"], 
    "content_scripts": [
      {
        "matches": ["https://mc.login.exacttarget.com/hub-cas/login*"], 
        "js": ["content.js"]
      }
    ]
  }
  

Second is the JavaScript:

// Function to set a cookie with a specified name, value, and expiration in days
function setCookie(name, value, days) {
  const date = new Date();
  date.setTime(date.getTime() + days * 24 * 60 * 60 * 1000);
  const expires = "expires=" + date.toUTCString();
  document.cookie = name + "=" + value + ";" + expires + ";path=/";
}

// Function to extract the username when the form is submitted
function handleLogin() {
  // Select the username input field; adjust the selector to match the SFMC login page
  const usernameField = document.querySelector("input[name='username']");
  console.log("The username is :"+usernameField);
  if (usernameField) {
    const username = usernameField.value;

    // Set a cookie with the username, valid for 7 days
    setCookie("ActiveUser", username, 7);
    console.log(`Cookie set: ActiveUser=${username}`);
  }
}

// Attach the handler to the login form submit event
document.addEventListener("DOMContentLoaded", () => {
  const loginForm = document.querySelector("LoginForm"); // Adjust if needed
  if (loginForm) {
    loginForm.addEventListener("submit-btn", handleLogin);
  }
});

Somehow its not creating cookie as expected. i am not sure what i am doing wrong

When i go to inspect in chrome , i was expecting a cookie with name as ActiveUser be there