Why does not authorize by session?

Question

Sessions

LAMP, the session is created (cookie too, the browser sees it), but authorization does not occur. Where to look for the reason? Everything works fine on the other server.

Answer 1

I don't like comments of a detailed kind, but... To begin with, it's worth highlighting the problem more widely: where it works, software versions (most likely PHP versions), where it doesn't work, software versions, etc. Now the question looks like: "Why is the lamp in the room not on? The switch is working ... In the entrance, the same lamp is on normally"