Paypal failing on confirm to own website - but only for some users/shipping info not transferring

Using eCart6.

I have asked a number of people to test that my setup to Paypal Express Checkout is working - after a lot of moving and adjusting of code it works for me on all browsers, works for one other person on IE and FF, correctly ending on checkout_success.php, sending the confirmation email and inserting data into the orders table.

For everyone else, the process fails after they have successfully completed their details on PayPal and click continue to redirect to the originating website for completion, where it ends on cart.php with the message "cart is empty" - which suggests to me that it's not the paypal transaction that's failing, but something in eCart.

I'm beyond frustrated as I can't see how it can be a browser or server issue when it works perfectly for some and not for others.

Secondary (?) information, which also needs to be resolved - shipping information is not prepopulating paypal shipping form (not that I can find out whether it is even supposed to), nor is it showing on confirmation page or email. I have changed form field bindings to pre-populate with database info after users login, and wonder if that is the issue there.

I'm already a week overdue with this job and a speedy resolution would help a lot - thanks.

Checkout pages are attached privately.

Please provide a Skype username or a US phone number and a good time to contact you when you will be in front of your computer and we will have an engineer contact you to resolve this issue over the phone.

We are available Monday - Friday from 9am - 4pm EST (except major U.S. holidays).

Thanks Jason, I am available today from 11.30am NZDT. See pm for skype name.

I'm very confused by your two different time availabilities (9-4 EST in your message, and 9-5 PST on your help page) so will just say that I'm available NZDT Saturday 15th March between 8.30am to 8.30pm, if you can give me around 30 mins prior notice of a time. Urgent help would be much appreciated.

Please refer to yesterday's pm for skype details.

thanks
Sylvia

I am on the East Coat, web Assist main Offices are on the West Coast, my availability is 9-4 EST

see pm

Hi again Jason, I have found some more anomalies in the code that could be causing the problem(s). I will get back to you when I have made the changes needed and let you know whether I still need help.

Thanks
Sylvia

OK, send a message through skype is you still need help.

For the issue you are reporting where some users are getting a failure on directing back from paypal, this is probably a case of domain switching.

when items are added to the cart, they are stored in a session.

If the user browses to your site using the domain name without www in front and starts adding items:
http://mydomain.com/shop.php

and is then redirected to the pp_confirm page with www in front of the address:

http://www.mydomain.com/pp_confirm.php

this is considered 2 separate domains and 2 separate sessions. to prevent this, you can use htaccess to force the address to always point to www:
http://www.htaccessbasics.com/force-www-nonwww-domain/