Elissa’s answer to “I'd like very much to read your book Elizabeth Darcy returns, but on amazon it isn't available on k…” > Likes and Comments

From what I could tell in a brief online search the problem could be you have to buy the book on Amazon app, not on your Kindle reader.
After I read info I remembered I had that problem myself before my son bought me an I-Pad for Christmas. Amazon customer service does answer the phone if this continues.