Why does Firebase Auth UI always direct to the account creation page despite an account with the email existing?

Question

I have implemented the Firebase Auth UI for my web application. The initial process of creating an account works fine and is logged to the record but when I attempt to then use that email address to login I am again prompted to create an account? I am learning and new to firebase so I'm just getting to grips with things. Maybe I am implementing this incorrectly?

index.js

import { initializeApp } from "firebase/app";
import { getAuth, EmailAuthProvider } from "firebase/auth";
import * as firebaseui from 'firebaseui'
import firebaseConfig from './firebase-config.js'

// Initialize Firebase
const appInstance = firebaseConfig.appInstance;
const auth = getAuth(appInstance);

// Initialize the FirebaseUI Widget using Firebase.
var ui = new firebaseui.auth.AuthUI(auth);

ui.start('#firebaseui-auth-container', {
    signInOptions: [
      {
        provider: EmailAuthProvider.PROVIDER_ID,
        requireDisplayName: false
      }
    ],
    signInSuccessUrl: '/editor.html',
});

I have tried using incognito mode to ensure fresh browser test sessions along with creating new emails each time to test with. I made sure these accounts were created within the Firebase console. Rebuilding/restarting has not improved this behavior.