Why is collectstatic only detecting admin static files?

Question

I'm using S3 to store my static files, but I'm having an issue where only the admin static files are uploading to the bucket.

I expected to see the css and other folders from inside static upload to the bucket, but instead, this is all I got:

static/
- admin/
- flags/

What can I do to get my app's static folder to upload also?

Looking at other answers to this question, it seems like the main difference is that my project uses django-sass-processor, but I'm not sure why that would mean my entire folder is not picked up.

Project folder structure:

backend/
- accounts/
- core/
-- settings.py
-- ...
- static/
- templates/

settings.py

USE_S3 = os.getenv('USE_S3') == 'TRUE'

if USE_S3:
    # aws settings
    AWS_ACCESS_KEY_ID = os.getenv('AWS_ACCESS_KEY_ID')
    AWS_SECRET_ACCESS_KEY = os.getenv('AWS_SECRET_ACCESS_KEY')
    AWS_STORAGE_BUCKET_NAME = os.getenv('AWS_STORAGE_BUCKET_NAME')
    AWS_DEFAULT_ACL = 'public-read'
    AWS_S3_CUSTOM_DOMAIN = f'{AWS_STORAGE_BUCKET_NAME}.s3.amazonaws.com'
    AWS_S3_OBJECT_PARAMETERS = {'CacheControl': 'max-age=86400'}
    # s3 static settings
    AWS_LOCATION = 'static'
    STATIC_URL = f'https://{AWS_S3_CUSTOM_DOMAIN}/{AWS_LOCATION}/'
    STATICFILES_STORAGE = 'storages.backends.s3boto3.S3Boto3Storage'
else:
    STATIC_URL = '/staticfiles/'
    STATIC_ROOT = os.path.join(BASE_DIR, 'staticfiles')

STATICFILES_FINDERS = [
    'django.contrib.staticfiles.finders.AppDirectoriesFinder',
    'sass_processor.finders.CssFinder',
]

SASS_PROCESSOR_ROOT = os.path.join(BASE_DIR, 'static')


STATICFILES_DIRS = (os.path.join(BASE_DIR, 'static'),)

MEDIA_URL = '/media/'
MEDIA_ROOT = os.path.join(BASE_DIR, 'media')