How to remove drm from ebooks

My oneplusone worked very fine on my frtizbox 5490UE, but now I got a new fritzbox 7590LN and he asks permanently for the password and I can't get connected.

@Lakotaubp

I work on dev, so perhaps I try on stable

I used my BQ Aquarius m10 tablet to make pictures, but since one month the app on the tablet doesn't work anymore. How to test or the camera is broken or the app doesn't work right?