If your PDF did not convert properly the first time, that might be because of a metadata error so in this case we recommend using this link to reconvert your flipbook. That will use a different method of conversion and the fixer works on most corrupted PDF files.
Please be very careful as it will remove all hyperlinks from your PDF, but you can add them later in the content editor.
In order to use it correctly, you will have to grab your share link on your collections page then add that link in the box then hit Convert.
Here's a short tutorial on how to do that: