I tried all the possible situations and discovered some things.
1. I have translated the addition into Greek.Something is wrong with that language. Sometimes the notification comes and sometimes it doesn’t. Also, in Greek language, it is too late for the e-mail to arrive in my mail box and if notification arrives, you will arrive after 5 minutes.
2. When I return to the English language, the notification works correctly and you arrive 10 seconds after the order confirmation.
3. In English language works fine, all you need to do is login to the admin panel. Only that. Even if you have minimized the browser, the notification works.
Settings
RestroPress–> Settings –> General –> Order Notification
Enable Notification (cheked)
Notification sound (upload some mp3 file)
Play notification sound in loop (cheked)
Notification Length = 60