It looks like you have the ID column in the shopping cart set up to be a number, but you are actually entering a text value. That is causing the code to write:
$eCart1_itemID = floatval("".$row_rsATC['ProductID'] ."");
and it makes it so the itemID isn't recognized. If you update the cart object and specify the ID column as text and then re-apply the server behavior that line should update to:
$eCart1_itemID = "".$row_rsATC['ProductID'] ."";
and I believe that would work correctly.