ASUS MeMO Pad 10 with Swedish operating system no longer authorized Adobe DRM. Why?

I have been using this unit to read e-books for months but suddenly it does not work anymore. The Adobe DRM does not work and when I try to register another one I get error message: It is not possible to authorize the unit. I am using an ASUS MeMO Pad 10 with Swedish operating system and Aldiko Book Reader. Android-version 4.2.2