In Django 2.2 / Python 3.7.2 i'm getting the error

[Sany07]

in admin.py file this error occurs.

from config.models import SiteConfiguration
ModuleNotFoundError: No module named 'config'

[linevych]

I assume config is your application where you placed you, singleton model.
This is not a django-solo issue but the way how do you structure your project, please provide your INSTALLED_APPS and your project structure.

Also, it always better to use relative imports instead of absolute imports if you importing within one application:

# config/admin.py
from .models import SiteConfiguration

[Sany07]

Problem solved.

Thank You :)