Frontend not communicating with Backend

I've got my final year web application project from someone who developed it from me, the front end is in react and backend is in python django with database sqlite. According to him the project is complete and error free and requires no changes to be made as he tested it thoroughly, now for some reasons i dont have his contact or whereabouts so i cant really contact him. I've exhausted all my options but my front end refuses to communicate with backend. Homepage loads fine. but it wont redirect to any other page, it just refreshes to homepage again, if i try to sign in it will always say invalid email or password. if i try to sign up it just refreshes back to homepage after hitting submit. I've done everything from ensuring cors relation, to running production builds, to ensuring urls.py is as it should be. It just wont work. I npm run build my front end and then copy build folder to my backend root directory. then i npm start my front end and py manage.py runserver my backend at the same time, they both compile without any errors and exceptions, my frontend also opens my homepage, my backend also open my homepage on seperate localhosts, backends localhost/admin and other pages of django works fine, but for some reasons i just cant make my front end functional. i'm so exhausted and so concerned because i have to submit my project in 2 days time. i've exhausted my options with chat GPT. i would be very thankful for your help.
Here's the link to my backend https://github.com/choudhrydaniyal/BackEnd

And here's link to my frontend https://github.com/choudhrydaniyal/FrontEnd

This is the code of my settings.py file(only the relevant code).

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'rest_framework_simplejwt',
    'api',
    'rest_framework',
    'djoser',
    'corsheaders',
    'backend',
    'rest_framework_simplejwt.token_blacklist',
]

CORS_ALLOWED_ORIGINS = [
    'http://localhost:3000',
    'http://localhost:8000',
    'http://127.0.0.1:8000',
    'http://localhost:8080',
    'http://127.0.0.1:3000',
    'https://fakenewsdetectionteam.herokuapp.com',
]

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': BASE_DIR / 'db.sqlite3',
    }
}

STATIC_URL = '/static/'
STATICFILES_DIRS = [
    os.path.join(BASE_DIR, 'build/static')
]
STATIC_ROOT = os.path.join(BASE_DIR, 'static')
MEDIA_URL = '/media/'
MEDIA_ROOT = os.path.join(BASE_DIR, 'media')
DOMAIN = ('localhost:3000/#')

And this is the code of my urls.py file.

urlpatterns = [
    path('admin/', admin.site.urls),
    path('auth/', include('djoser.urls')),
    path('auth/', include('djoser.urls.jwt')),
    path('auth/', include('djoser.social.urls')),
    path('news/',views.Postdata.as_view()),
    path('news/<int:id>',views.Postdata.as_view()),
    path('list',views.get_trends.as_view()),
    path('profile',views.get_profile.as_view()),
    path('postprofile',views.ProfileViewSet.as_view()),
]

urlpatterns += static(settings.MEDIA_URL,document_root=settings.MEDIA_ROOT)
urlpatterns += [re_path(r'^.*', TemplateView.as_view(template_name='index.html'))]

1. Check the network tab in your browser's developer tools to see if any requests are failing or returning errors. This may help you identify specific API requests that are not working correctly.

2. Try running the frontend and backend on different ports, and update the API URLs in your frontend code accordingly. This can help isolate any issues related to CORS or port conflicts.

3. Check your backend logs for any error messages related to incoming requests. This may help you identify issues with authentication or request validation.

4. Try running the frontend and backend on the same domain (e.g. by using a reverse proxy like nginx). This may help avoid any issues related to CORS.

5. Check if there are any environment variables that need to be set for your application to work correctly. For example, if your application requires a secret key or database URL, make sure these are set correctly in your environment.
   --If these things does work use trouble shoot frame works like post man and Sentry