Additional Information: If I de-authorize (delete the authorization) I can see all the books.
Authorize his Digital Edition.
Closed the Programm.
Rename the my Digital Edition folder under your documents.
Start Digital Edition.
Download you eBook.
Thank you very much. Doing so, I found a book which caused the Problems. Not importing the book solved the issue. Thanks again for your help and best Regards. Rolf
You are welcome.