can't open EPUB3 book in ADE on Android tablet

I have installed ADE on my old Android phone and can open EPUB3 books with no problems.

I have also installed ADE on a newer Android tablet but there ADE wont open the same EPUB3 books.

All books are without DRM.

ANY ideas what I am doing wrong?

Should ADE run on all Android versions or only on some?

thanks for helping!