Ensure that the admin app is present in the INSTALLED_APPS list in your settings.py file:

INSTALLED_APPS = [
    'django.contrib.admin',  # Ensure this line is present
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    # other apps...
]

If the issue persists, please provide more details about the error or your project structure.