django-cors-headers is not working

[GaganSingh]

I'm using django-cors-headers in order to work it with react js.
Here's my settings.py:-

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'django_cleanup.apps.CleanupConfig',
    'myapp',
    'corsheaders'
]
MIDDLEWARE = [
    'corsheaders.middleware.CorsMiddleware',
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]
CORS_ALLOWED_ORIGINS = [
    "http://127.0.0.1:3000"
]

I'm running my react app at http://127.0.0.1:3000 but I'm still getting

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://127.0.0.1:8000/api/categories. (Reason: CORS header 'Access-Control-Allow-Origin' missing).

What could be the reason for the error?

[Adam Johnson]

Use the network inspector to check the response headers. Or use curl and set the Origin header appropriately. Read the linked articles.

[PraneethG]

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:7000/api/jwt/create/. (Reason: expected ‘true’ in CORS header ‘Access-Control-Allow-Credentials’).