How to get signals.py executed in django?

I run the following signals.py on (Ubuntu2204/WSL2 Windows 11) using Django 4.1.1 / Python 3.10

from .models import Sale
from django.db.models.signals import m2m_changed
from django.dispatch import receiver


@receiver(m2m_changed, sender=Sale.positions.through)
def calculate_total_price(sender, instance, action, **kwargs):
    print('action', action)

    total_price = 0
    if action == 'post_add' or action == 'post_remove':
        for item in instance.get_positions():
            total_price += item.price
    
    instance.total_price = total_price
    instance.save()

apps.py already signals in VSCode that signals is not used, this is also confirmed in the Django Debug Toolbar

from django.apps import AppConfig


class SalesConfig(AppConfig):
    #default_auto_field = 'django.db.models.BigAutoField'
    name = 'sales'

def ready(self):
    import sales.signals

and then the __init__.py file

default_app_config = 'sales.apps.SalesConfig'

settings.py looks like this:

"""
Django settings for reports_proj project.

Generated by 'django-admin startproject' using Django 4.1.1.

For more information on this file, see
https://docs.djangoproject.com/en/4.1/topics/settings/

For the full list of settings and their values, see
https://docs.djangoproject.com/en/4.1/ref/settings/
"""

from pathlib import Path

# Build paths inside the project like this: BASE_DIR / 'subdir'.
BASE_DIR = Path(__file__).resolve().parent.parent


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/4.1/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = "django-insecure-dbl^hk-m6-dz01+1i*hi5#rz4t90(y5s-cls1&0js5hj^ojo70"

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True

ALLOWED_HOSTS = []


# Application definition

INSTALLED_APPS = [
    "django.contrib.admin",
    "django.contrib.auth",
    "django.contrib.contenttypes",
    "django.contrib.sessions",
    "django.contrib.messages",
    "django.contrib.staticfiles",
    "debug_toolbar",
    # my apps
    "customers",
    "products",
    "profiles",
    "reports",
    "sales.apps.SalesConfig",
    # 3rd party
    "crispy_forms",
]

CRISPY_TEMPLATE_PACK = "bootstrap4"

MIDDLEWARE = [
    "django.middleware.security.SecurityMiddleware",
    "django.contrib.sessions.middleware.SessionMiddleware",
    "django.middleware.common.CommonMiddleware",
    "django.middleware.csrf.CsrfViewMiddleware",
    "debug_toolbar.middleware.DebugToolbarMiddleware",
    "django.contrib.auth.middleware.AuthenticationMiddleware",
    "django.contrib.messages.middleware.MessageMiddleware",
    "django.middleware.clickjacking.XFrameOptionsMiddleware",
]

ROOT_URLCONF = "reports_proj.urls"

TEMPLATES = [
    {
        "BACKEND": "django.template.backends.django.DjangoTemplates",
        "DIRS": [BASE_DIR / 'templates'],
        "APP_DIRS": True,
        "OPTIONS": {
            "context_processors": [
                "django.template.context_processors.debug",
                "django.template.context_processors.request",
                "django.contrib.auth.context_processors.auth",
                "django.contrib.messages.context_processors.messages",
            ],
        },
    },
]

WSGI_APPLICATION = "reports_proj.wsgi.application"


# Database
# https://docs.djangoproject.com/en/4.1/ref/settings/#databases

DATABASES = {
    "default": {
        "ENGINE": "django.db.backends.sqlite3",
        "NAME": BASE_DIR / "db.sqlite3",
    }
}


# Password validation
# https://docs.djangoproject.com/en/4.1/ref/settings/#auth-password-validators

AUTH_PASSWORD_VALIDATORS = [
    {
        "NAME": "django.contrib.auth.password_validation.UserAttributeSimilarityValidator",
    },
    {
        "NAME": "django.contrib.auth.password_validation.MinimumLengthValidator",
    },
    {
        "NAME": "django.contrib.auth.password_validation.CommonPasswordValidator",
    },
    {
        "NAME": "django.contrib.auth.password_validation.NumericPasswordValidator",
    },
]


# Internationalization
# https://docs.djangoproject.com/en/4.1/topics/i18n/

LANGUAGE_CODE = "en-us"

TIME_ZONE = "UTC"

USE_I18N = True

USE_TZ = True


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/4.1/howto/static-files/

STATIC_URL = '/static/'
STATICFILES_DIRS = [
    BASE_DIR / 'static',
    BASE_DIR / 'sales' / 'static',
]

MEDIA_URL = '/media/'
MEDIA_ROOT = BASE_DIR / 'media'

# Default primary key field type
# https://docs.djangoproject.com/en/4.1/ref/settings/#default-auto-field

DEFAULT_AUTO_FIELD = "django.db.models.BigAutoField"

INTERNAL_IPS = [
    "127.0.0.1",
]

Any hint would be highly appreciated, the code looks ok to me it must be some dependency issue but I have no idea where to start looking really