Is this for one of your books you sold digitally? The revival of wisdom?
Did you have permission from the author and publisher to sell this item digitally?
the item if you did have permission was listed incorrectly as digital items need to be listed in the category everything else not books as you did.
your item specifics state it’s a paperback book. So a buyer is within their rights to claim item not received although buried in your listing it states it’s a pdf file.
finally you may want to consider changing your user name. I am sure that would potentially put buyers off.