Django Admin - Cannot Login with Superuser

Question

There are a few questions on this topic, but none of them solved my challenge. I cannot login to Django Admin with a correct username and password.

settings.py:

import os
from django.core.exceptions import ImproperlyConfigured

BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))

def get_env_variable(variable_name):
    try:
        return os.environ[variable_name]
    except KeyError:
        error_msg = 'Set the {} environment variable'.format(variable_name)
        raise ImproperlyConfigured(error_msg)


SECRET_KEY = get_env_variable('SECRET_KEY')

DEBUG = False

ALLOWED_HOSTS = ['XXXXXXXX']

INSTALLED_APPS = [
    'dal',
    'dal_select2',
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'alerts.apps.AlertsConfig',
    'widget_tweaks',
]

SESSION_COOKIE_SECURE = False
SESSION_EXPIRE_AT_BROWSER_CLOSE = True

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.auth.middleware.RemoteUserMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]

AUTHENTICATION_BACKENDS = [
    'django.contrib.auth.backends.ModelBackend',
    'django.contrib.auth.backends.RemoteUserBackend',
]

ROOT_URLCONF = 'myProject.urls'

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

WSGI_APPLICATION = 'myProject.wsgi.application'

DATABASES = {
    'default': {
        'ENGINE': 'XXXXXXXXXXx',
        'HOST': get_env_variable('DATABASE_HOST'),
        'NAME': get_env_variable('DATABASE_NAME'),
        'USER': get_env_variable('DATABASE_USERNAME'),
        'PASSWORD': get_env_variable('DATABASE_PASSWORD'),
        'OPTIONS': {
            'driver': 'XXXXXXXXXXX'
        },
    },
}

# Password validation
# https://docs.djangoproject.com/en/1.11/ref/settings/#auth-password-validators
AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]

LANGUAGE_CODE = 'en-us'

TIME_ZONE = 'UTC'

USE_I18N = True

USE_L10N = False

DATE_FORMAT = "m/d/Y"

USE_TZ = True

STATIC_ROOT = os.path.abspath(os.path.join(BASE_DIR, 'myProject', 'static'))
STATIC_URL = '/static/'
STATICFILES_DIRS = []

SECURE_CONTENT_TYPE_NOSNIFF = True
SECURE_BROWSER_XSS_FILTER = True
CSRF_COOKIE_SECURE = False
X_FRAME_OPTIONS = 'DENY'

I have tried turning on and off the various security settings. I have access to the DB, and the superuser exists and is staff. When I attempt to login, the DB table says the superuser logged in at that time, but the browser won't go beyond the splash page and says the username/password are incorrect. Other staff members (i.e. not superusers) can login. I think the problem might reside in the fact that I am using a RemoteUser backend in addition to the Model backend, but I'm not sure.

Why can't my superuser login?