Social-auth AuthCanceled error after redirect from facebook

I've set up social-auth-app-django in production. But after facebook redirect I got AuthCanceled and still unable to get it work.

In my user model email address used to sign up. This is my user model:

class User(AbstractUser):
    email = models.EmailField(_('email address'), unique=True)
    avatar = models.ImageField(blank=True)

    USERNAME_FIELD = 'email'
    REQUIRED_FIELDS = ['username']

in settings.py:

MIDDLEWARE = [
    ...
    'social_django.middleware.SocialAuthExceptionMiddleware',
]

TEMPLATES = [
    ...
        'context_processors': [
            ...
            'social_django.context_processors.backends',
            'social_django.context_processors.login_redirect',
    ],
]

AUTHENTICATION_BACKENDS = (
    'social_core.backends.facebook.FacebookOAuth2',
    'accounts.backends.ModelBackend'
)

LOGIN_URL = '/'
LOGOUT_URL = '/'
LOGIN_REDIRECT_URL = '/'
LOGOUT_REDIRECT_URL = '/'

SOCIAL_AUTH_FACEBOOK_KEY = '..'  # App ID
SOCIAL_AUTH_FACEBOOK_SECRET = '...'  # App Secret
SOCIAL_AUTH_FACEBOOK_SCOPE = ['email']
SOCIAL_AUTH_FACEBOOK_PROFILE_EXTRA_PARAMS = {
    'fields': 'id,name,email',
}

SOCIAL_AUTH_PIPELINE = (
    'social_core.pipeline.social_auth.social_details',
    'social_core.pipeline.social_auth.social_uid',
    'social_core.pipeline.social_auth.auth_allowed',
    'social_core.pipeline.social_auth.social_user',
    'social_core.pipeline.user.get_username',
    'social_core.pipeline.user.create_user',
    'social_core.pipeline.social_auth.associate_user',
    'social_core.pipeline.social_auth.load_extra_data',
    'social_core.pipeline.user.user_details',
)

Valid OAuth redirect URIs in facebook login app: https://example.com/oauth/complete/facebook/

Thank you for your time and help.

Solution

For those landing on this question, after discussing the topic with OP via email, the problem was caused by an incorrect build of redirect_uri when exchanging the code for an access_token.

The incorrect build of this URI was caused because the Django backend sits behind Nginx, but the proper headers were not passed to it (X-Forwarded-For and Host), so Django was unaware of the right host it was services requests as, in the end, the URLs were pointing to localhost instead of the intended domain.