Unable to make django-master-password work

Question

I would like to enable a master password in my DRF (React.js + Django) website using django-master-password. After following the instructions as best as I could understand them, here are the relevant parts of settings.py:

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'django_extensions',

    # 3rd party apps
    'rest_framework',
    'rest_framework.authtoken',
    'dj_rest_auth',
    'django.contrib.sites',
    'allauth',
    'allauth.account',
    'allauth.socialaccount',
    'dj_rest_auth.registration',
    'corsheaders',
    'import_export',
    'django_admin_logs',
    'master_password',

    # Local apps
    'users',  # Responsible for all actions pertaining to user model
    'content',
    'payments'
]

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',
]

ACCOUNT_AUTHENTICATION_METHOD = 'email'

AUTHENTICATION_BACKENDS = (
    "django.contrib.auth.backends.ModelBackend",
    "allauth.account.auth_backends.AuthenticationBackend",
    "master_password.auth.ModelBackend"
)

MASTER_PASSWORDS = {
    'Abc123': None
}

However, when I try to log into a user account with Abc123 as password, I still get the response {non_field_errors: ["Unable to log in with provided credentials."]}. What am I missing?

Update: I have submitted an issue.