Automatic deactivation when opening the second e-book (.epub format)

Every time I activate my Adobe ID, I open the first book and can see the text. After closing that book, by the opening of the second one I get a white screen. It does not matter which books I do open, and they are all in .epub format. Then I go to the DRM Settings menu and there is my account deactivated, without my knowledge.

Every time I do activate my account, there is the same story. As such, Adoble Digital Editions is unusable...

Please help. Thanks.