After testing on dummy store, I have migrated live site to FC2 : saladseminars.com
Vanilla FC2 with custom cart include based on tiered flat rate shipping as per test store.
But on live site products are not stored between product pages, e.g.
page 1 - add product - cart shows content correct with product 1
page 2 - add product - cart only shows product 2, and product 1 has gone
I added the sample code line
<!-- FOXYCART -->
<script src="//cdn.foxycart.com/salad/loader.js" async defer></script>
<!-- /FOXYCART -->
into product page
Only difference from test and live site is that live uses Perch and Foxycart addon
But can't see that is causing problem
Help to diagnose and resolve much appreciated - live site is only partly live !