Why don't push notifications always come?

Question

PHP

The mechanism is implemented according to the article https://habr.com/ru/post/357862/
Step 11: Sending a notification from the backend:
everything works from the console, when sent from the browser (via the nginx server), the script does not return errors, everything is the same, but push notifications do not come. I suspect that some configs are needed, or even modules for the http server.