Redis – flask sessions not persistent between requests from cross domains

I have a frontend vue site hosted on google’s firebase with the url (https://front-end.web.com) , while my flask backend is hosted on heroku with the url (https://back-end.heroku.com). This makes my session not to persist across requests, I tried fixing this by implementing CORS on my backend, but for some reason it’s not working , below are snippets of my code to show my implementation

config_class.py

class ConfigClass():
    CORS_ALLOW_HEADERS = ['Content-Type']
    CORS_ORIGINS = ['https://front-end.web.com']
    SECRET_KEY = os.environ.get("APP_SECRET_KEY")
    SESSION_TYPE = 'redis'

_init.py

from flask import Flask, session
from flask_session import Session
from flask_cors import CORS


from root_folder.config import ConfigClass


db = SQLAlchemy() 
migrate = Migrate() 
ma = Marshmallow()  
sess = Session()


def create_app(ConfigClass):

    # initiate the flask app and assign the configurations #
    app = Flask(__name__)
    app.config.from_object(config_options[config_class])
    sess.init_app(app)

    from root_folder.clients import clients_app

    # register all the blueprints in this application
    app.register_blueprint(clients_app)

    CORS(app, supports_credentials=True)

    # return the app object to be executed
    return app

app.py

from root_folder import create_app

app = create_app()

Procfile:

web: gunicorn -w 1 app:app

axios front end request

let formData = new FormData();
formData.append("email", email);
formData.append("password", password);

axios.post(
                backendUrl+'create_client_account',
                formData,
                {
                    withCredentials: true,
                    headers:{
                       "Content-Type": "multipart/form-data"
                    }
                }
);

create client route ( I have stripped this code block to the bare minimum to make it understandable):

from flask import session

# route for creating account credentials
@bp_auth_clients_app.route("/create_client", methods=["POST"])
def create_client():
    
    username = request.form.get("username").lower()
    email = request.form.get("email").lower()

    
    # create account code goes here  #
    
    auth_authentication = True

    session["auth_authentication"] = auth_authentication

    req_feedback = {
            "status": True,
            "message": "Account was successfully created",
            "data": feedback_data
    }

    return jsonify(req_feedback), 200

After the account is successfully created, I am unable to access the session value in subsequent requests, it returns None.

To recreate the problem on my local server, I access the front-end via the domain "localhost:8080" , while I access the flask server via "127.0.0.1:8000" . If I change the front end domain to "127.0.0.1:8080", I don’t usually have any problems.

Kindly advice on what to do.