So as a debug step, add at the start of the page code
session_start();
var_dump($_SESSION);and see what it says. Either it’s not saving properly (your first bit of code in #3 seems OK), or it’s not retrieving properly, or it’s not displaying properly. So the above would show if it can be retrieved, so the next thing would be to put a var_dump($_SESSION); just before you draw the form and see if it’s still there.