Seit 10 Tagen kann ich keine Bücher öffnen, es kommt die Meldung user unknown was kann ich tun

Hi Rosemarier,

From the details shared above, I assume that you are trying to open a e-book using Adobe Reader DC app? Have you ever been able to open these books earlier?

If yes, then you must try the repair the of application. Open app>Help>Repair Installation.

However, you should use the Adobe Digital Edition which is a supporting application to open the Ebooks.

You can download it form Adobe Digital Editions | Download

Regards,

Akanchha