Periodic tasks in Django are not called

Question

I use django_crontab to periodically call my tasks. The problem is that periodic tasks are not called.

I created a test function that sends me a message and I can understand that the task is done:

def test_crj():
    send_message("Test cronjobs!")

I set it to run once every five minutes:

# in settings.py
INSTALLED_APPS = [
    ... ,
    "django_crontab",
]
CRONJOBS = [
    ("*/5 * * * *", "project.cronjob.test_crj", '>> /tmp/test.log'),
]

crontab sees it:

> docker exec container python3.9 manage.py crontab show
# Currently active jobs in crontab:
# a35573388f4e46c33f88fc825f0a1d8f -> ('*/5 * * * *', 'project.cronjob.test_crj', '>> /tmp/test.log')

> docker exec container crontab -l
# */5 * * * * /usr/local/bin/python3.9 /app/manage.py crontab run a35573388f4e46c33f88fc825f0a1d8f >> /tmp/test.log # django-cronjobs for project

But nothing happens! Meanwhile, when I run the function independently, everything works fine. And when I run it the way the system crontab should run (as I understand it), it works too.

> docker exec container python3.9 manage.py crontab run a35573388f4e46c33f88fc825f0a1d8f
# it works

What could be the error and who is to blame - django_crontab or the system crontab? Or where and how do I look at the logs, why it doesn't work?