I can't download a book. Instead I see an error that says "This XML file does not appear to have any style information associated with it." What can I do?

Sometimes when a Leanpub reader or author tries to download a book, they get this error:

This XML file does not appear to have any style information associated with it. The document tree is shown below.

If you are a Leanpub reader and you are seeing this error, please contact us at hello@leanpub.com with a link to the page where you are getting this error, when you try to click the download link. If you could specify the exact link you are clicking on, that will help us resolve the issue more quickly.

If you are a Leanpub author and you are seeing this error for one of your own books, please contact us at hello@leanpub.com with a link to the page where you are getting this error, when you try to click the download link. If you could specify the exact link you are clicking on, that will help us resolve the issue more quickly. Also, if you are using our Upload writing mode, where you upload ebook files you have created yourselves, please provide us with copies of the same files you tried to upload, that are showing this behavior. That will let us test the files directly, and hopefully find a solution a lot faster!

I just bought a book package with Extras to download. Where do I download the Extras?

There doesn't seem to be that much security around download links...?

I want to see error reports when I generate a book. How can I do this?

I can't sign in and I'm seeing a message about CAPTCHA. What can I do to log in?

I don't see any download links when I select a book in my Leanpub library. What can I do to download the book?