This issue is caused when your web server isn't properly configured to handle sessions. Sessions are how PHP remembers things like what a customer puts in their cart, subtotals, totals, and other important information. Some server administrators elect to turn sessions off by default, but will enable them upon request.
Please contact your web server administrator and ask them to enable PHP sessions for your website, and then try to use your shopping cart again.
After you create a cart and upload it with our software, we have a test script you can access to double-check that your server is compatible. You can access this script at: http://[CARTPATHURL]/ccdata/php/servertest.php
When you go to the above script, if you see an error that looks like the text below, contact your hosting provider and give them the above information:
FAILED - this server can not store cart data for users.