I uploaded two books to XinXii on December 19 and 20 respectively and both were shipped to Casa del Libro and Barnes & Noble on January 10, Normally, they ship faster, so I suspect that XinXii had an extended holiday break. Both books shipped on January 10 were already available at Casa del Libro today.
As for Barnes & Noble, they are just slow period and it usually takes about a month for books reported as shipped to show up in the store. I have a book that was shipped to B&N on December 16 (and B&N needed two weeks to approve the book, whereas Casa del Libro managed to approve it in approx. 3 days and had it available in their store after another day or two), but still isn't available in their store. So in short, Barnes & Noble is just a mess, regardless whom you use to distribute to them.
As for XinXii sales, I get the occasional sale there, though it's not a whole lot. German books seem to do better at XinXii than English books, though one of my German titles doesn't sell there at all, although it's my second best selling German title at Amazon. Different audiences, I guess.