Help - Add Album To Cart

I've install 'Cart' and 'Zip Download' but every time I clicked 'Add Album To Cart' in the left menu bar or before the thumbnails, I got the messages,

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Items Currently in Your Cart
Your cart is empty.

To add items, browse the gallery and select 'Add to cart' from the item's action menu.
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I can download the 'zip photos' after user logon.
Is it possible to do this withoug logon ?

Can anyone help ?
Thanks.