Persistent authorization page in IPad

I've Adobe Digital Editions installed in a MacBook Pro and it works perfectly. I can open and read all the files installed. Now, I'm trying to access to the same contents through and Ipad, so I've downloaded the App and I've shared the files through the itunes application. The files are appearing in the IPAd. When I try to open them I get a message to authorize, then I introduce my username and password and it seems to be OK. I come back to the library, double click a book and the same authorization page appears (in this case to ask if I want to deauthorize). The same occurs with any of the books. Please, any idea? What is the problem?