I'm having a similar set of frustrations. I think it's related to virtual domain name. In any event, I'm changing to a cookie less approach. Here's the deal:
look for a system variable like: $PHPSESSID - you should see it when you look at the data from the phpinfo()
Then, make a table with that as its key. Well, any new page you go to during one explorer or navigator window's life will have a constant session id - so this lets you read & write data so you can 'carry it' from screen to screen.
It sounds harder than it is & like most things, you'll look back at it & wonder why it wasn't obvious! & like most things before you get there, it's a nightmare & it challenges your self image😉