item per page missing itemid value

[nickel21]

The default sef create link like the following
index.php?option=com_virtuemart&Itemid=&keyword=&limit=15&view=category&virtuemart_category_id=71&lang=el
and don't include the itemid value in the item per page selection
the virtuemart product have itemid correct and in the categories doesn't not exist at all .
I need this itemid value for create sef url using sh404
what should do for fix the issue
Many thanks in advance