eCart & DFP downloads: db updated, but download not working

Hello

Thanks for all the help so far.

Test site: http://taom.co.uk/resources/.
DW CS4 on WinXPSP3 / PHP / MySQL
WA products: eCart4.5.2, Cookies3.1.2, DFP2.0.2, DA2.0.6, SA1.1.8

1. I've followed the 'How to set up a Download Centre' recipe, but the download buttons aren't doing anything.
   
   
2. Data are being written to the user, order and orderdetails tables in the WA eCommerce database, and payment is taken by PayPal.
   
   
3. The checkout_success.php page has a link to the Download Centre (for which I've followed the How To).
   
   
4. The Download Centre was showing no records until I added the eCart server behaviour to that page, then a number of orders appeared, but with no functionality from the download buttons. Since then, the number of orders has remained the same (even though more orders are being written to the database). As there is a red exclamation marked next to the eCart server behaviour on the Download Centre page, perhaps it shouldn't be there.
   
   
5. The ProductLocation for the download files is outside the webroot, so the path in DFP is '../../downloads'. I assume that there are other customers using WA products for this purpose with 1and1 (Linux) hosting.

To cut to the chase, I'm wondering if the problem is that the session or order isn't being carried through from the checkout_success page to the Download Centre. The Order History page isn't showing any records at all.

At one point I had wondered if the checkout_success page should double up as the Download Centre, but I guess that would require an if-else statement -- to avoid showing checkout info when the Download Centre is accessed at other times than after an order -- and perhaps is making the whole exercise more difficult than it need be!

I'd be grateful for some guidance to help me see where I'm going wrong.

Thanks!
Alistair