Firstly, you need to know that your Kobo Aura supports only EPUB, PDF, and MOBI eBooks, TXT, HTML, XHTML, and RTF text files and CBZ and CBR Comic Books. I recommend you check the file format of your book by right-clicking its icon and opening the General tab. If the file should be supported by the device, I recommend you upgrade Adobe Digital Editions to the latest version and transfer again the book. If this doesn't help, try resetting the device using the instructions that you can find in its manual. Also, you can contact the manufacturer and ask for the resetting steps.