Did it caused by the DRM protection? If so, I think you can try some eBook DRM removal software, like Calibre or ePubor eBook DRM Removal (ePubor ebook Converter and eBook DRM Removal software) . The Calibre is freeware, but you have to install another plugin to remove the DRM. ePubor is a shareware, which will cost nearly $45. But it can bypass the DRM protection from any eBooks with few clicks. Hope it's helpful.