It appears that there is no awareness of currently owned resources on the Verbum November Free Book of the Month page. I'm logged on and all of the "Add to cart" buttons are blue. I clicked to add several of them to my cart to which the page indicated they were added. But when I went to my cart the page said that items were removed because you already own them. (I knowing did that to make note of the behavior of the website.)
I do appreciate the last check, but it seems a waste of time and effort. I know the catalog knows what you own already and gray's that button out. Should be able to do that here as well.
https://verbum.com/monthly-sale#free