New Android phones can't sign in to their account, nor create new ones
I can't give much details about it unfortunately as I do not own one myself.
However I think many could confirm that it's happening to the latest Android phones that ChatSecure just can't connect to the Internet regardless of what you do. I tried to help my friends but there was nothing that really made a difference for them. Any other smartphone worked great instead. It happened to a Nexus and an Asus, using Android 6.0.