When executing (in TERMINAL)
python manage.py startapp (your_app_name)
First check apps.py in (your_app_name) folder.
It should be something like this:
class (__auto_generated__)Config(AppConfig): default_auto_field = 'django.db.models.BigAutoField' name = '(your_app_name')
Second check settings.py, in INSTALLED_APPS['']
, you must have 'your_app_name'
Be careful when you change your app names