Philip Clarke and I have spent a week working on this problem, and he has finally worked out what has gone wrong ish. I will post the message below and others can reply about this probelm if its affecting them.

Quote Originally Posted by Philip Clarke

FOUND THE BUG.

The bug is in the ip addressing system. If the information that I have used to bypass the system is set up to be sent from a different ip address as would be the case in worldpay, then your ZC installation redirects to a timed out / log in again page, which is why worldpay is not recreating the session and it's not hitting the module. It's stopping before. Now evither you are running Suhoisin and something strange is going on (because normally it would not respond to one test that I have already done, where it passed) or you have change the session settings that you sent the the screen shot of. If you haven't changed the configuration settings, and the system is still set to check ip address "false" then I would also suggest turning off the "ip to host conversion", even though in theory it has bugger all to do with it and testing again.

Basically although the bug is found, and is simply that the sessions are not being recreated from a differing ip address without the need to log in. The bug is not Solved. That will take a lot more work and going through the whole session handling system to try and work out why it is not responding to the the database settings. It may also be worth setting the db Check ip address to True, saving it, and setting it to false, in case there is something in the database that is not correct, or if ZC has done something to look for "true" instead of "True" or "False" instead of "false", of it maybe that the database is blank and just displays "False" in the row on your screen, but the code is actually looking for the word "false".

It would still be worth doing a survey on the forum as to when this issue affected people because then it may be possible to isolate the part of code responsible more quickly. I can solve it, but it will take time and FTP access. You can forget about putting that file into place now. I must consider what I should do since it's not a module problem, its a Zen cart problem and they kicked me out.