On my computer I have 3 Pythons, a 3.6 from Anaconda, and a 2.7 & 3.7 that are regular python. Prompted by a nudge from this GH issue, I switched from the Anaconda 3.6 to the 3.7, and back again, and the problem went away.

I think that this is the case because your .vscode/settings.json (the following is mine), doesn't have that last line until you change your python, at which point, that last line is put in and Pyright has something to look at.

{
  "python.linting.enabled": true,
  "python.formatting.provider": "black",
  "python.pythonPath": "C:\\Users\\ben\\Anaconda3\\python.exe"
}

You should create a pyrightconfig.json file or pyproject.toml file at the root of your project. For example, if it's a Django project, you should have one of those files where manage.py is placed. Then, set include parameter and add the subdirectories (or app folders in Django terms).

You can consult this sample config file. See this issue ticket.

For example, if this were my project structure:

├── manage.py
├── movie
│   ├── admin.py
│   ├── apps.py
│   ├── __init__.py
│   ├── models.py
│   ├── tests.py
│   └── views.py
├── moviereviews
│   ├── asgi.py
│   ├── __init__.py
│   ├── settings.py
│   ├── urls.py
│   └── wsgi.py
└── pyproject.toml

my pyproject.toml would be:

[tool.pyright]
include = ["movie", "moviereviews"]

If you are working within a Python virtual environment, set venvPath and venv. Consult the documentation for an exhaustive list of options.