Not really sure where this question fits, but I've been having issues lately with posting books on my bookshelf to sell. One book I tried and the ISBN number pulls up a completely nonexistent book for the author. It's Laughing Out Loud by Kody Keplinger but lists it as Sonny by Kody Keplinger (this is frustrating because there is a member wishing for that book but I have no way to contact them to see if they're actually wishing for LOL or this 'Sonny' book that does not exist). I also tried posting another book but there's no record of it in paperback form on the site, just hardcover. Do we have to submit requests to get them listed on PBS or do we consider it unlistable and just put it in the forum under 'Unpostable'?

You can post them yourself using the ‘post without ISBN’ button. That generates a unique PBS ISBN and you’ll need to enter book details yourself. Also check inside the book on the publisher’s page, sometimes alternate ISBNs are listed there.

Some publishers reuse ISBNs so what is happening with those books is not unusual. If the other versions are WL you can start a thread in the Book Bazaar forum stating your shelf has those books that are WL under a different ISBN (give the WL ISBN for reference) & perhaps someone will order the non-WL ones from you.