When you try to checkout a Kindle title, if you see an error page like this:
or like this:
this means Amazon probably no longer offers this title in the Kindle format. To report this problem, on your Loans page, click the Report Kindle Book problem link:
While waiting for this problem to be fixed, you can still enjoy this title by reading it in your browser on your Kindle Fire, desktop, laptop, or phone. Click the Read now in browser button to read this title in your browser.