Problems to send ebook to eReader Tagus.

Hello. I installed the Adobe Digital Edition app without problems and I have it authorized; I don't have problems downloading ebooks on the PC or reading them on it, but when I send them to my eReader "Tagus" I have problems because when I open an ebook the pages are empty. My eReader "Tagus Iris" supports the DRM format. I do not know what is the problem.

Thank you very much.

Maria Luisa.